Boiler Fault Code Search: Worcester, Baxi, Ideal & More

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Showing 259 of 259 codes

Worcester Bosch 67 codes

Worcester Bosch boiler fault codes
Code	What it means	What you can do
Greenstar i ErP (Greenstar 25i / 30i combi)
FA 306	A flame (ionisation) signal was detected after the gas valve closed. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
EA 227	No flame was detected after ignition, so the boiler locked out. · Greenstar i	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
F7 228	A flame signal was detected before the burner started. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
EA 229	The flame signal was lost while the boiler was running. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F0 238	Gas valve or control box error. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
A1 281	The pump appears to be stuck or running dry. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E9 276	The primary flow temperature went above 95 °C. · Greenstar i	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
E9 224	The flue thermostat or the high-limit (overheat) thermostat has opened. · Greenstar i	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
D4 341	The primary flow temperature is rising too quickly. · Greenstar i	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
C7 214	The fan did not run during start-up. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
C6 215	The fan is running too fast. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
C6 216	The fan is running too slowly. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
C7 217	The fan stopped while the boiler was running. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
C1 264	The fan stopped during operation. · Greenstar i	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E2 222	The flow temperature sensor reads as a short circuit. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E2 223	The flow temperature sensor is disconnected. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E2 350	Flow temperature sensor short circuit (second sensor code). · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E2 351	Flow temperature sensor disconnected (second sensor code). · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
CC 800	Outdoor weather sensor fault (only shown when an outdoor sensor accessory is connected). · Greenstar i	Engineer after one reset Nothing urgent: the boiler normally keeps heating without the outdoor sensor, using a fixed setting. Press reset once to see if it clears.
A7 808	Hot water temperature sensor fault. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
Fd 231	The power was interrupted while the boiler was already locked out. The previous lockout code is the real fault. · Greenstar i	Safe checks first Look for the code shown before Fd and use that code's advice. If the gas is on and pressure is fine, press reset once.
EA 261	The boiler's code plug (HCM) may be faulty. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
9U 233	The control box or the code plug (HCM) is faulty or loose. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
C4 237	The control box or code plug (HCM) is faulty. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F0 239	The control box or code plug (HCM) is faulty. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F0 242	The control box or code plug (HCM) is faulty (the manual groups cause codes 242 to 256 together). · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
b7 257	The control box or code plug (HCM) is faulty. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F0 258	The control box or code plug (HCM) is faulty. The manual also lists this cause with display code EH. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F1 259	The control box or code plug (HCM) is faulty. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F0 262	The control box or code plug (HCM) is faulty. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F1 263	The control box or code plug (HCM) is faulty. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F0 272	The control box or code plug (HCM) is faulty. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F0 280	The control box is faulty. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F0 290	Control box fault (analogue/digital reference error). · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
A8 361	The fitted code plug (HCM) does not match the control box or display. · Greenstar i	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
C4 273	The boiler has run continuously for 24 hours and is pausing for a short self-check. · Greenstar i	Safe checks first Nothing to do. The boiler pauses for a few minutes after 24 hours of non-stop running and then carries on.
Greenstar 4000 (GR4700iW C combi)
227	The boiler tried to light but did not detect a flame after ignition, so it locked out. · Greenstar 4000	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
228	The boiler is seeing a flame signal when there should not be a flame. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
234	The boiler has detected an electrical fault with the gas valve. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
269	A fault has been detected in the flame monitoring circuit. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
306	A flame signal is still detected after the gas supply has been shut off. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
363	System fault in the boiler electronics linked to flame (ionisation) measurement. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
2916	The gas valve was detected as open during the post-purge period. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
2920	Fault in the flame monitoring system. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
2923	Unexpected feedback from the modulating gas valve. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
281	The pump appears to be stuck or running with air instead of water. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
1017	Maintenance warning: system water pressure is too low. · Greenstar 4000	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
224	A safety overheat device on the flue or heat exchanger has tripped. Short-lived it blocks the boiler; if it persists it becomes a lockout. · Greenstar 4000	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
214	The fan stopped while the boiler was in its ignition safety period, so the boiler locked out. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
2910	The boiler has detected a problem in the flue system. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
2915	The fan keeps running after the post-purge period has ended. · Greenstar 4000	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
1021	Fault with the hot water temperature sensor; hot water is affected. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
1037	Outdoor (weather) sensor fault; the boiler runs in a back-up heating mode. · Greenstar 4000	Engineer after one reset Nothing urgent: the boiler normally keeps heating without the outdoor sensor, using a fixed setting. Press reset once to see if it clears.
1065	The system pressure sensor is faulty or not connected. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
1073	The flow temperature sensor reads as a short circuit. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
1074	No signal from the flow temperature sensor (open circuit). · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
1075	The heat exchanger temperature sensor reads as a short circuit. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
1076	The heat exchanger temperature sensor is disconnected. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
233	The boiler's identification (code) plug or electronics are not recognised. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
235	The software versions of the boiler electronics and the code plug do not match. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
238	The boiler electronics have reported a fault, which the manual links to the gas valve circuit. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
242	Internal system fault in the boiler electronics. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
360	System fault in the boiler electronics, linked by the manual to the code plug. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
2085	Internal fault in the boiler. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
2908	System fault in the burner controller. · Greenstar 4000	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
232	The boiler is being held off by an external switching contact. · Greenstar 4000	Safe checks first Check any external control wired to the boiler, such as a timer, frost stat or switch, is on.
1010	The boiler has lost communication with a connected control over the EMS bus. · Greenstar 4000	Safe checks first Check your room thermostat or programmer has power or fresh batteries and is set to call for heat. For a wireless control, follow its guide to reconnect it. Then press reset once.

Baxi 52 codes

Baxi boiler fault codes
Code	What it means	What you can do
Baxi 600 Combi 2 (24 / 30 / 36)
H.03.02	The flame was lost temporarily. · 600 Combi 2	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
H.03.54	Temporary flame loss, or shutdown because the supply voltage is too low. · 600 Combi 2	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
E.01.04	The flame was lost five times in 24 hours with the burner on, so the boiler locked out. · 600 Combi 2	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
E.04.10	The burner failed to light after four attempts. This is the 600 Combi 2's ignition lockout. · 600 Combi 2	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
E.04.12	Ignition failure while checking for a parasitic (false) flame. · 600 Combi 2	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E.04.17	Fault in the gas valve control circuit. · 600 Combi 2	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E.04.54	Fault in the gas valve control circuit. · 600 Combi 2	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
A.02.06	Warning: water pressure in the heating system is low. · 600 Combi 2	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
H.00.42	The pressure sensor is open circuit or faulty (shown while a reset is in progress). · 600 Combi 2	Engineer after one reset Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
H.01.05	The temperature difference between flow and return has reached its maximum. · 600 Combi 2	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
H.01.18	No water circulation was detected (temporary). · 600 Combi 2	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
H.02.07	Pressure in the heating circuit is low (the boiler stops until it is restored). · 600 Combi 2	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
E.01.17	No water circulation (permanent lockout). · 600 Combi 2	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
H.01.08	The heating flow temperature rose too quickly; the boiler pauses for 10 minutes. · 600 Combi 2	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
H.01.14	The maximum flow temperature has been reached. · 600 Combi 2	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
H.01.21	The flow temperature rose too quickly in hot water mode; the boiler pauses for 10 minutes. · 600 Combi 2	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
E.04.03	The maximum flow temperature has been exceeded. · 600 Combi 2	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
E.04.08	The maximum safe temperature has been reached (the safety thermostat has acted). · 600 Combi 2	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
E.01.20	The maximum flue gas temperature has been reached. · 600 Combi 2	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E.04.13	The fan blade is blocked. · 600 Combi 2	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E.04.15	The flue gas exhaust pipe is blocked. · 600 Combi 2	Safe checks first From outside, look at the flue terminal without touching it and make sure nothing is covering it, such as a bag, snow, a nest or stored items. In freezing weather, check the condensate pipe and thaw it with warm (not boiling) water. Press reset once. Do not touch or adjust any flue parts.
A.00.34	The boiler expects an outdoor sensor but cannot detect one. · 600 Combi 2	Engineer after one reset Nothing urgent: the boiler normally keeps heating without the outdoor sensor, using a fixed setting. Press reset once to see if it clears.
E.00.04	The return temperature sensor is disconnected. · 600 Combi 2	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E.00.05	The return temperature sensor is short circuited. · 600 Combi 2	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E.00.20	The flue gas temperature sensor is short circuited or reading below range. · 600 Combi 2	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E.00.21	The flue gas temperature sensor is reading above range. · 600 Combi 2	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E.01.12	The return sensor is reading hotter than the flow sensor. · 600 Combi 2	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E.04.01	The flow temperature sensor is short circuited. · 600 Combi 2	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E.04.02	The flow temperature sensor is disconnected. · 600 Combi 2	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
H.03.05	The power supply voltage is too low. · 600 Combi 2	Safe checks first Check whether lights are dimming or other appliances are struggling. If they are, contact an electrician or your electricity network operator (call 105 for a power cut). Then press reset once.
E.02.17	Permanent communication failure between the gas valve and the main board. · 600 Combi 2	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
H.02.09	A blocking input or frost protection is active, so the boiler is partly stopped. · 600 Combi 2	Safe checks first Check any external timer, thermostat or frost control connected to the boiler is on. The code clears itself when the input is released.
H.02.10	A blocking input signal has stopped the boiler completely. · 600 Combi 2	Safe checks first Check any external timer, thermostat or control connected to the boiler is on. The code clears itself when the input is released.
Baxi 600 Combi (624 / 630, first generation)
E09	Gas valve connection cable fault. · 600 Combi (624/630)	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E15	Gas valve fault. · 600 Combi (624/630)	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E128	Flame failure during normal operation. · 600 Combi (624/630)	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
E133	Interruption of the gas supply or flame failure: the boiler could not light or prove a flame. · 600 Combi (624/630)	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
E135	Interruption of the gas supply, listed in the manual as an internal error. · 600 Combi (624/630)	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
E384	False flame: a flame signal is detected when there should be none. · 600 Combi (624/630)	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E109	Pre-circulation fault: the boiler did not see water circulating before lighting. · 600 Combi (624/630)	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E118	Primary system water pressure is too low (the manual says below 0.5 bar). · 600 Combi (624/630)	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
E125	Circulation fault in the primary circuit. The manual says it shows if the water temperature hardly changes 15 to 30 seconds after lighting, or overshoots the set temperature by 30 °C twice within 10 minutes. · 600 Combi (624/630)	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E270	Circulation fault (dry fire): the boiler detected it was firing without enough water flow. · 600 Combi (624/630)	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E110	The safety (overheat) thermostat has operated: the primary water overheated. · 600 Combi (624/630)	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
E130	The flue NTC has operated (flue overheat). · 600 Combi (624/630)	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E160	Fan or fan wiring fault. · 600 Combi (624/630)	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E20	Central heating (flow) NTC sensor fault. · 600 Combi (624/630)	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E28	Flue NTC sensor fault. · 600 Combi (624/630)	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E40	Central heating return NTC sensor fault. · 600 Combi (624/630)	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E154	Flow/return sensor temperature test fault. · 600 Combi (624/630)	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E321	Hot water NTC sensor fault. · 600 Combi (624/630)	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E83	Communication error. · 600 Combi (624/630)	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.

Ideal 31 codes

Ideal boiler fault codes
Code	What it means	What you can do
Ideal Logic Max Combi C (C24 / C30 / C35, IE edition manual)
F2	Flame loss. · Logic Max Combi C	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
L2	Ignition lockout: the boiler failed to light. · Logic Max Combi C	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
L6	False flame lockout. · Logic Max Combi C	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F1	Low water pressure. · Logic Max Combi C	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
FU	Flow/return temperature difference greater than 50 °C. · Logic Max Combi C	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
L1	Flow temperature overheat or no water flow. · Logic Max Combi C	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
F3	Fan fault. · Logic Max Combi C	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F4	Flow thermistor fault. · Logic Max Combi C	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
L4	Flow thermistor fault (locking version). · Logic Max Combi C	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F5	Return thermistor fault. · Logic Max Combi C	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
L5	Return thermistor fault (locking version). · Logic Max Combi C	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F6	Outside sensor failure. · Logic Max Combi C	Engineer after one reset Nothing urgent: the boiler normally keeps heating without the outdoor sensor, using a fixed setting. Press reset once to see if it clears.
FA	Negative flow/return thermistor differential: the return reads hotter than the flow. · Logic Max Combi C	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F7	Low mains voltage. · Logic Max Combi C	Safe checks first Check whether lights are dimming or other appliances are struggling. If they are, contact an electrician or your electricity network operator (call 105 for a power cut). Then press reset once.
F9	Unconfigured or faulty PCB, or a gas valve short circuit. · Logic Max Combi C	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
L9	Unconfigured or faulty PCB, or a gas valve short circuit (locking version). · Logic Max Combi C	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
LC	Five boiler resets within 15 minutes. · Logic Max Combi C	Safe checks first Stop resetting. Switch the boiler off at its mains switch, wait at least 15 minutes, then check the gas supply and pressure before trying one more reset.
Ideal Logic Combi (24 / 30 / 35)
F2	Flame loss. · Logic Combi	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
L2	Flame loss lockout (this manual lists L2 alongside F2 as flame loss). · Logic Combi	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
L6	False flame lockout: a flame was detected when there should not be one. · Logic Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F1	Low water pressure. · Logic Combi	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
L1	Flow temperature overheat or no water flow. · Logic Combi	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
F3	Fan fault. · Logic Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F4	Flow thermistor fault. · Logic Combi	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F5	Return thermistor fault. · Logic Combi	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F6	Outside sensor failure. · Logic Combi	Engineer after one reset Nothing urgent: the boiler normally keeps heating without the outdoor sensor, using a fixed setting. Press reset once to see if it clears.
F7	Low mains voltage. · Logic Combi	Safe checks first Check whether lights are dimming or other appliances are struggling. If they are, contact an electrician or your electricity network operator (call 105 for a power cut). Then press reset once.
F9	Unconfigured PCB. · Logic Combi	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
C0	BCC (boiler chip card) activation fault. · Logic Combi	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
C2	BCC (boiler chip card) fault. · Logic Combi	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
L5	Five boiler resets within 15 minutes. The boiler blocks further resets. · Logic Combi	Safe checks first Stop resetting. Switch the boiler off at its mains switch, wait at least 15 minutes, then check the gas supply and pressure before trying one more reset.

Viessmann 26 codes

Viessmann boiler fault codes
Code	What it means	What you can do
Vitodens 050-W (BPJC) and Vitodens 100-W (B1HA / B1KA)
E5	Internal fault; the burner is blocked. · Vitodens 050-W/100-W	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F3	A flame signal is already present when the burner starts. · Vitodens 050-W/100-W	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F4	No flame signal detected: the boiler failed to light. · Vitodens 050-W/100-W	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
F8	The fuel (gas) valve closes too late. · Vitodens 050-W/100-W	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E3	Fault in the safety chain; the burner is in a fault state. · Vitodens 050-W/100-W	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
F1	Maximum flue gas temperature exceeded. · Vitodens 050-W/100-W	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
F2	The temperature limiter (overheat stat) has tripped. · Vitodens 050-W/100-W	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
F9	Fan speed too low during burner start. · Vitodens 050-W/100-W	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
FA	The fan did not reach its idle (stopped) state. · Vitodens 050-W/100-W	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
FC	Electrical fan control in the control unit is faulty. · Vitodens 050-W/100-W	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
10	Outside temperature sensor short circuit. The boiler keeps running at a constant temperature. · Vitodens 050-W/100-W	Engineer after one reset Nothing urgent: the boiler normally keeps heating without the outdoor sensor, using a fixed setting. Press reset once to see if it clears.
18	Outside temperature sensor lead break. The boiler keeps running at a constant temperature. · Vitodens 050-W/100-W	Engineer after one reset Nothing urgent: the boiler normally keeps heating without the outdoor sensor, using a fixed setting. Press reset once to see if it clears.
30	Boiler water temperature sensor short circuit. The burner is blocked. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
38	Boiler water temperature sensor lead break. The burner is blocked. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
50	Cylinder temperature sensor short circuit; no hot water heating (100-W manual). · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
51	Hot water outlet temperature sensor short circuit; no hot water heating. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
52	Flow sensor short circuit. The burner is blocked. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
58	Cylinder temperature sensor lead break; no hot water heating (100-W manual). · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
59	Hot water outlet temperature sensor lead break; no hot water heating. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
5A	Flow sensor lead break. The burner is blocked. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
b0	Flue gas temperature sensor short circuit. The burner is blocked. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
b8	Flue gas temperature sensor lead break. The burner is blocked. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F0	Internal fault; the burner is blocked. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
Fd	Burner control unit fault. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
FF	Burner control unit fault. · Vitodens 050-W/100-W	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
A9	Communication error with an OpenTherm control; the boiler runs without it. · Vitodens 050-W/100-W	Safe checks first Check your room thermostat or programmer has power or fresh batteries and is set to call for heat. For a wireless control, follow its guide to reconnect it. Then press reset once.

Vaillant 34 codes

Vaillant boiler fault codes
Code	What it means	What you can do
ecoTEC plus (VU / VUW ..6/5-5, combi and system)
F.26	Fault: the gas valve stepper motor is not working or not connected. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.27	Safety shut-down: flame simulation. The flame sensor reports a flame that should not be there. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.28	Start-up failure: ignition unsuccessful. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.29	Operating failure: the flame went out and re-ignition failed. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.54	Fault at boiler start: no or insufficient gas inlet pressure. · ecoTEC plus	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
F.61	Fault: the gas valve cannot be actuated. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.62	Fault: the gas valve is slow to shut off after the flame goes out. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.67	Implausible flame signal. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.68	Unstable flame signal. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.92	Incorrect gas type: the coding resistor does not match the gas group entered. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.93	Combustion quality outside the permitted range. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.22	Safety shut-down: low water pressure. · ecoTEC plus	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
F.23	Safety shut-down: the flow/return temperature difference is too large (water circulation too low). · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.73	The water pressure sensor reports the pressure as too low (signal too weak). · ecoTEC plus	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
F.74	The water pressure is too high (sensor signal too strong). · ecoTEC plus	Engineer after one reset Read the gauge. If it is above about 2.5 bar, check the filling loop is fully closed. Do not try to release water from the boiler yourself.
F.75	Pump or water shortage: no pressure rise detected when the pump starts. · ecoTEC plus	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
F.83	NTC temperature gradient fault: the flow and return barely changed when the burner fired. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.20	Safety shut-down: the temperature limiter acted because the flow or return temperature got too high. · ecoTEC plus	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
F.24	Safety shut-down: the temperature is rising too fast. · ecoTEC plus	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
F.25	Safety shut-down: flue gas temperature too high. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.32	Fan fault: the fan is faulty or not connected. · ecoTEC plus	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.00	Flow temperature sensor interruption: the sensor is faulty or not connected. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.01	Return temperature sensor interruption: the sensor is faulty or not connected. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.10	Flow temperature sensor short circuit. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.11	Return temperature sensor short circuit. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.13	Cylinder or warm-start sensor short circuit. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.71	The flow temperature sensor is returning implausible values. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.72	The temperature difference between the flow and return sensors is too great. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.85	Flow and return sensors fitted incorrectly. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.49	eBUS fault: under-voltage on the control bus. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F.63	EEPROM fault. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F.64	Electronics or safety-relevant sensor fault. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F.65	Electronics temperature fault: the electronics are faulty or too hot. · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F.70	Invalid device specific number (DSN). · ecoTEC plus	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.

Glow-worm 30 codes

Glow-worm boiler fault codes
Code	What it means	What you can do
Glow-worm Energy7 combi (25c / 30c / 35c-A)
F.27	Safety shut-down: fault in flame detection (a flame is detected when there should be none). · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.28	Ignition unsuccessful when starting. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.29	Flame loss during operation. · Energy7	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
F.61	Gas valve assembly control fault. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.62	Gas valve switch-off control fault: the valve shuts off late. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.67	Implausible flame signal returned to the electronics. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.68	Unstable flame signal. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.87	Electrode fault: electrodes not connected, connected wrongly or shorted. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.88	Gas valve assembly not connected, connected wrongly or shorted. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.22	Safety shut-down: not enough water in the boiler (low pressure). · Energy7	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
F.23	Safety shut-down: the flow/return temperature difference is too large. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.73	Water pressure sensor not connected or short circuited. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.75	Pressure sensor fault: no pressure rise seen when the pump starts. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.83	Dry fire: little or no temperature change at the flow or return sensor when the burner starts. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.89	Pump not connected or connected wrongly. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.20	Safety shut-down: overheating temperature reached. · Energy7	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
F.24	Safety shut-down: the temperature rose too fast. · Energy7	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
F.25	Safety shut-down: flue gas temperature too high. · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.32	Fan fault (the manual also notes the fan frost protection function). · Energy7	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
F.00	Flow temperature sensor fault (open circuit). · Energy7	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.01	Return temperature sensor fault (open circuit). · Energy7	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.10	Flow temperature sensor short circuit. · Energy7	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.11	Return temperature sensor short circuit. · Energy7	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.71	Flow or return temperature sensor stuck at a constant value. · Energy7	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
F.49	eBUS fault: voltage too low. · Energy7	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F.63	EEPROM fault. · Energy7	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F.64	Electronics, sensor or analogue-to-digital converter fault. · Energy7	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F.65	Electronics temperature too high. · Energy7	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F.70	Invalid product code (DSN). · Energy7	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.
F.97	Main PCB self-test failed. · Energy7	Engineer after one reset Write down the full code. Check the boiler has power and nothing else in the house has tripped, then switch the boiler off and on at its mains switch or press reset once. If the code comes back, leave the boiler off.

Potterton 19 codes

Potterton boiler fault codes
Code	What it means	What you can do
Potterton Assure Combi (25 / 30 / 36)
E09	Gas valve connection cable fault. · Assure Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E15	Gas valve fault. · Assure Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E128	Flame failure during normal operation. · Assure Combi	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
E133	Interruption of the gas supply or flame failure: the boiler could not light or prove a flame. · Assure Combi	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
E135	Interruption of the gas supply, listed in the manual as an internal error. · Assure Combi	Safe checks first Check another gas appliance such as the hob works, the gas meter valve is on and, on a prepayment meter, there is credit. In freezing weather, check the plastic condensate pipe outside: if it is frozen, pour warm (not boiling) water along it. Then press reset once. If the code comes back, stop resetting.
E384	False flame: a flame signal is detected when there should be none. · Assure Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E109	Pre-circulation fault: the boiler did not see water circulating before lighting. · Assure Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E118	Primary system water pressure is too low (the manual says below 0.5 bar). · Assure Combi	Safe checks first Look at the pressure gauge while the boiler is cold. If it is below about 1 bar, top it up with the filling loop exactly as your user guide shows, to about 1–1.5 bar or the figure in your guide, then close the loop fully. Check the radiator valves are open, then press reset once.
E125	Circulation fault in the primary circuit. The manual says it shows if the water temperature hardly changes 15 to 30 seconds after lighting, or overshoots the set temperature by 30 °C twice within 10 minutes. · Assure Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E270	Circulation fault (dry fire): the boiler detected it was firing without enough water flow. · Assure Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E110	The safety (overheat) thermostat has operated: the primary water overheated. · Assure Combi	Engineer after one reset Let the boiler cool for 20 to 30 minutes, then press reset once. If the code comes back, leave the boiler off.
E130	The flue NTC has operated (flue overheat). · Assure Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E160	Fan or fan wiring fault. · Assure Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.
E20	Central heating (flow) NTC sensor fault. · Assure Combi	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E28	Flue NTC sensor fault. · Assure Combi	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E40	Central heating return NTC sensor fault. · Assure Combi	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E154	Flow/return sensor temperature test fault. · Assure Combi	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E321	Hot water NTC sensor fault. · Assure Combi	Engineer after one reset Write down the full code. Check the boiler has power, then switch it off and on at its mains switch or press reset once. If the code comes back, leave it there: sensors are inside the casing.
E83	Communication error. · Assure Combi	Engineer after one reset There is no homeowner check that fixes this code. Write down the full code, press reset once, and if it comes back leave the boiler off.

How to read a boiler fault code

A fault code is the boiler telling you why it has stopped. Most codes fall into two kinds:

Blocking or temporary codes clear on their own once the cause goes away, for example when the pressure is topped up or a heat demand ends.
Lockout codes keep the boiler off until someone presses reset. Lockouts protect you from gas, flue or overheat problems, so reset only once.

Before you do anything, write down the brand, the model (on the front or the data label underneath) and the full code, including any letters, dots and numbers. The same code can mean different things on different brands, and sometimes on different models from the same brand.

How each brand shows its codes

Greenstar i ErP (Greenstar 25i / 30i combi): Greenstar i boilers show a two-character fault code (for example EA) and a three-digit cause code (for example 227). Quote both, e.g. 'EA 227'. The same layout is used across many Greenstar models, but always check your own manual.
Greenstar 4000 (GR4700iW C combi): The Greenstar 4000 shows a number (for example 227) with a short text description. A 'V' fault locks the boiler until it is reset; a 'B' fault clears itself when the cause goes away.
Baxi 600 Combi 2 (24 / 30 / 36): The 600 Combi 2 shows a letter, a group number and a specific number, e.g. E.04.10. H codes are temporary (the boiler restarts itself when the cause clears); E codes are permanent and need a reset; A codes are warnings.
Baxi 600 Combi (624 / 630, first generation): These Baxi combis flash an E symbol followed by a two- or three-digit number, e.g. E133.
Ideal Logic Max Combi C (C24 / C30 / C35, IE edition manual): Logic Max Combi C boilers that show codes use F (fault) and L (lockout) codes, e.g. L2. Newer Logic Max Combi 2 models show the fault in words instead (e.g. 'Ignition Lockout').
Ideal Logic Combi (24 / 30 / 35): The Logic Combi alternates two characters on its display, e.g. 'F' then '1' for F1.
Vitodens 050-W (BPJC) and Vitodens 100-W (B1HA / B1KA): Vitodens 050-W and 100-W boilers show a two-character code, e.g. F4. If 'R' or a reset symbol appears with it, the burner has locked out and needs a reset.
ecoTEC plus (VU / VUW ..6/5-5, combi and system): Vaillant boilers show F. followed by a number, e.g. F.28. S. codes are status codes, not faults.
Glow-worm Energy7 combi (25c / 30c / 35c-A): Glow-worm boilers show F. followed by a number, e.g. F.28, the same style as Vaillant (both are made by the Vaillant Group).
Potterton Assure Combi (25 / 30 / 36): The Assure Combi flashes an E symbol followed by a two- or three-digit number, e.g. E133.

What is safe for you to do

Every code here follows the same safety rules. You can:

press the reset button once, as your user guide shows;
for low-pressure codes, top up the pressure with the filling loop, as your user guide shows;
for ignition and flame-loss codes, check the gas is on at the meter and a prepayment meter has credit;
thaw a frozen plastic condensate pipe outside with warm (not boiling) water;
check the thermostat, timer and power to the boiler.

Never open the boiler casing. Only a Gas Safe registered engineer may work inside a gas boiler. Codes marked Engineer after one reset have no homeowner fix: reset once, then leave them to an engineer. Codes marked Safe checks first list the one check that relates to that code.

Common fault code questions

What does an ignition lockout mean on a boiler?

An ignition lockout means the boiler tried to light the burner, did not detect a flame and shut itself down for safety. Common causes include no gas getting through, a frozen or blocked condensate pipe, or a worn ignition or flame-sensing part. Do the safe checks, reset once, then call a Gas Safe engineer.

Why is my boiler showing a temperature fault?

Temperature or overheat faults are often caused by poor water circulation, low pressure, air, sludge or a sensor problem. Check pressure and that radiator valves are open, then reset once. If it returns, book a Gas Safe engineer, as pump or sensor checks need the casing opened.

Why is my boiler showing a fan fault?

A fan fault means the boiler cannot confirm the fan is running at the right speed or air is moving through the flue. Check the flue outside is not blocked by leaves, a nest or snow. Reset once. If it returns, a Gas Safe engineer needs to test the fan.

Why is my boiler showing a sensor or thermistor fault?

Boilers use temperature sensors, also called thermistors, to control and protect the burner. A sensor fault means a reading is missing or out of range, from a failed sensor or loose wiring. There is nothing safe to fix yourself beyond one reset. Book a Gas Safe engineer.

Can the same fault code mean different things on different boilers?

Yes. Codes such as F1 or E9 mean different things between brands, and even between ranges from the same brand. Always check the code against the manual for your exact model, and give the engineer your model and GC number as well as the code.

My boiler shows a code I cannot find. What should I do?

Write down the code exactly, including any letters, dots and numbers, and check the user guide for your exact model, which is on the data badge. Do the basic safe checks. If the code is not listed or keeps returning, book a Gas Safe engineer and give them the full code.

Why does my boiler only work after I reset it?

If a boiler runs after every reset but keeps locking out, there is an underlying fault, such as an ignition, flue, pressure or sensor problem. Keep a note of the code or light pattern and how often it happens, then book a Gas Safe engineer.

Why is my boiler display flashing but no code shows?

Some boilers use a flashing light instead of a number to signal a lockout. Check the user guide for your model to read the pattern. Do the basic checks and reset once, then call a Gas Safe engineer if it returns.

Code still showing? Book a repair

CombiCert Ltd is a Gas Safe registered business (621146) in Telford, Shropshire. Our team of 2 to 5 engineers is led by director and Gas Safe engineer Peter Jefferson. Boiler repair from £90 + VAT, parts quoted separately.

Send us the make, model and the exact code on WhatsApp and we will tell you what we need to check.

Boiler repairs WhatsApp us Call 07393 220694

Manuals used

Every explanation is written in our own words from these manufacturer installation and service manuals. Codes we could not check against a manual are left out. If your model is not listed, check its own manual or ask us.

Greenstar i ErP (Greenstar 25i / 30i combi): Greenstar i ErP Installation, Commissioning and Servicing Instructions, doc. 6 720 806 944 (2016/07), pp. 65–68, section 8.1.2 Error codes (Table 48). PDF (manufacturer copy)
Greenstar 4000 (GR4700iW C combi): Greenstar 4000 Installation and Maintenance Instructions (GR4700iW C), doc. 6 720 891 161 (2021/10) UK/IE, pp. 71–75, section 10.1.2 Operating/Fault code table. PDF (manufacturer copy)
Baxi 600 Combi 2 (24 / 30 / 36): Baxi 600 Combi 2 Installation and Service Manual & Boiler Fiche, doc. 7796561-03 (04/23), pp. 73–77, section 11.2 Error codes (Tab. 33 and Tab. 34). PDF (manufacturer copy)
Baxi 600 Combi (624 / 630, first generation): Baxi Combi 624–630 Installation and Service Manual, doc. 7679306-1 (10/08/2017), p. 64, section 10.1 Error codes (Fig. 69). PDF (trade-site copy)
Ideal Logic Max Combi C (C24 / C30 / C35, IE edition manual): Ideal Logic Max Combi C Installation & Servicing (C24IE, C30IE, C35IE), doc. UIN 223440 A05, User's section 8, Fault codes (PDF p. 80). PDF (trade-site copy)
Ideal Logic Combi (24 / 30 / 35): Ideal Logic Combi 24, 30, 35 Installation and Servicing (with User's Guide), doc. UIN 204626 A12 (January 2014), User's Guide p. 7 (PDF p. 71), Fault codes table. PDF (manufacturer copy)
Vitodens 050-W (BPJC) and Vitodens 100-W (B1HA / B1KA): Vitodens 100-W Type B1HA, B1KA Installation and Service Instructions; Vitodens 050-W Type BPJC Installation and Service Instructions, doc. 5677 216 GB (3/2015); 5513 085 GB (9/2014), 100-W pp. 62–65 'Fault display'; 050-W PDF pp. 46–49 'Fault display'. PDF · 050-W PDF (trade-site copy)
ecoTEC plus (VU / VUW ..6/5-5, combi and system): ecoTEC plus Installation and Maintenance Instructions (VU, VUW ..6/5-5), doc. 0020244997_07 (15.07.2021), pp. 60–62, Appendix E Overview of fault codes. PDF (manufacturer copy)
Glow-worm Energy7 combi (25c / 30c / 35c-A): Glow-worm Energy7 Installation and Maintenance Instructions, doc. 0020300875_01, PDF pp. 51–53, Appendix E Overview of fault codes. PDF (manufacturer copy)
Potterton Assure Combi (25 / 30 / 36): Potterton Assure Combi Installation and Service Manual, doc. 7717311-01, p. 64, section 10.1 Error codes (Fig. 68). PDF (trade-site copy)

Explanations are written by CombiCert from the manufacturer manuals listed above; check the manual for your exact model. This page is general information, not a diagnosis. If you smell gas, call 0800 111 999. Machine-readable data: fault-codes.json.

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