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boiler service, boiler repair, emergency repair
Vaillant Home Regular 15 A Boiler Fault Codes
| Code | Meaning | Possible Cause |
| F00 | Fault: Flow temperature sensor | NTC plug not plugged in or has come loose, multiple plug on the PCB not plugged in correctly, interruption in cable harness, NTC sensor defective |
| F01 | Fault: Return temperature sensor | NTC plug not plugged in or has come loose, multiple plug on the PCB not plugged in correctly, interruption in cable harness, NTC sensor defective |
| F10 | Short circuit: Flow temperature sensor | NTC sensor defective, short circuit in the cable harness, cable/casing |
| F11 | Short circuit: Return temperature sensor | NTC sensor defective, short circuit in the cable harness, cable/casing |
| F12 & F91 | Short circuit: Cylinder temperature sensor | NTC sensor defective, short circuit in the cable harness, cable/casing |
| F13 | Short circuit: Domestic hot water cylinder temperature sensor | NTC sensor defective, short circuit in the cable harness, cable/casing |
| F20 | Safety switch-off: Overheating temperature reached | Incorrect earth connection between cable harness and product, flow or return NTC defective (loose connection), black discharge via ignition cable, ignition plug or ignition electrode |
| F23 | Safety switch-off: Temperature difference too great (NTC1/NTC2) | Pump blocked, insufficient pump output, air in product, flow and return NTC sensors connected the wrong way round |
| F24 | Safety switch-off: Temperature rise too fast | Pump blocked, insufficient pump output, air in product, system pressure too low, non-return valve blocked/incorrectly installed |
| F25 | Safety switch-off: Flue gas temperature too high | Break in plug connection for optional flue gas safety temperature limiter (STB), break in cable harness |
| F27 | Safety switch-off: Fault in flame detection | Moisture on the electronics, electronics (flame monitor) defective, gas solenoid valve leaking |
| F28 | Fault: Ignition unsuccessful when starting up | Gas meter defective or gas pressure monitor has triggered, air in gas, gas flow pressure too low, thermal isolator device (TAE) has triggered, incorrect gas restrictor, incorrect spare gas valve, fault on the gas valve, multiple plug on PCB incorrectly plugged in, break in cable harness, ignition system (ignition transformer, ignition cable, ignition plug, ignition electrode) defective, ionisation current interrupted (cable, electrode), incorrect earthing of product, electronics defective |
| F29 | Fault: Flame loss | Gas supply temporarily stopped, flue gas recirculation, incorrect earthing of product, ignition transformer has spark failure |
| F32 | Fan frost protection function active: Fan speed outside the tolerance values | Plug on fan not correctly plugged in, multiple plug on PCB not correctly plugged in, break in cable harness, fan blocked, Hall sensor defective, electronics defective |
| F33 | Fan frost protection function active: Air pressure switch fault | Pressure monitor has not switched or has switched at a fan speed value that is too high (insufficient air supply) Pressure monitor plug not correctly plugged in, pressure monitor defective, hose removed from between the pressure monitor and silencer, air/flue pipe blocked |
| F49 | eBUS fault: Voltage too low | Short circuit on eBUS, eBUS overload or two power supplies with different polarities on the eBUS |
| F61 | Fault: Gas valve control system | Short circuit/short to earth in cable harness for the gas valve, gas valve defective (coils shorted to earth), electronics defective |
| F62 | Fault: Gas valve switch-off control | Delayed switch-off of gas valve, delayed extinguishing of flame signal, gas valve leaking, electronics defective |
| F63 | Fault: EEPROM | Electronics defective |
| F64 | Fault: Electronics/sensor/analogue-todigital converter | Flow or return NTC short circuited, electronics defective |
| F65 | Fault: Electronics temperature too high | Electronics overheating due to external influences, electronics defective |
| F67 | Value sent back by ASIC is incorrect (flame signal) | Implausible flame signal, electronics defective |
| F68 | Fault: Unstable flame (analogue input) | Air in gas, gas flow pressure too low, incorrect air ratio, incorrect gas restrictor, ionisation flow interruption (cable, electrode) |
| F70 | Invalid product code (DSN) | Display and PCB replaced at same time and Device Specific Number not reset, wrong or missing output range coding resistance |
| F71 | Fault: Flow/return temperature sensor | Flow temperature sensor signalling constant value: Flow temperature sensor incorrectly positioned on supply pipe, flow temperature sensor defective |
| F72 | Fault: Deviation in the water pressure sensor/return temperature sensor | Flow/return NTC temperature difference too great → flow and/or return temperature sensor defective |
| F77 | Fault: Condensate or smoke | No response, flue non-return flap defective |
| F78 | Interruption to DHW outlet sensor at external controller | UK link box is connected, but hot water NTC not bridged |
| F83 | Fault: Burner temperature sensor | Burner temperature sensor is defective When the burner starts, the temperature change registered at the flow or return temperature sensor is non-existent or too small: Insufficient water in the product, the flow or return temperature sensor is not in the correct position on the pipe |
| F84 | Fault: Flow/return temperature sensor | Values not consistent, difference < -6 K Flow and return temperature sensors signalling implausible values: Flow and return temperature sensors have been inverted, flow and return temperature sensors have not been correctly installed |
| F85 | Fault: Temperature sensor | The flow and/or return temperature sensors have been installed on the same pipe/incorrect pipe Temperature sensor not connected or is connected incorrectly |
| F86 | Fault: Underfloor heating contact | Underfloor heating contact open, sensor disconnected or defective |
| F87 | Fault: Electrodes | Electrodes not connected or they are connected incorrectly, short circuit in the cable harness |
| F88 | Fault: Gas valve | Gas valve not connected or it is connected incorrectly, short circuit in the cable harness |
| Connection | No communication between the PCB and the user interface | Electronics defective |