Vaillant boiler fault codes
| F.22 | This error code indicates a problem with low water pressure in the boiler system. You may need to check the pressure gauge on the boiler and adjust it to the correct level. |
| F.27 | This code means that there is a problem with the boiler’s ignition or flame sensing electrode. You may need to clean or replace the electrode, or contact a heating engineer for assistance. |
| F.28 | This error code indicates a problem with low water pressure in the boiler system. You may need to check the pressure gauge on the boiler and adjust it to the correct level. |
| F.32 | This code indicates a problem with the boiler’s flow sensor. You may need to clean or replace the sensor or contact a heating engineer to diagnose and fix the issue. |
| F.49 | eBUS fault – Short circuit on the eBUS, eBUS overload or two power supplies with different polarities on the eBUS |
| F.52 | Mass flow sensor connection fault – Mass flow sensor not connected/disconnected, plug not connected or incorrectly connected |
| F.53 | Mass flow sensor fault – Mass flow sensor faulty, filter below venturi filter cap wet or blocked, gas flow pressure too low |
| F.54 | Gas pressure fault (in combination with F.28/F.29)- No or too little gas supply pressure, gas valve closed |
| F.56 | Fault: Mass flow sensor regulation – Gas valve defective, cable harness to gas valve defective |
| F.57 | Fault during comfort safety mode – Ignition electrode highly corroded |
| F.61 | Fault: Gas valve regulation – Short circuit/short to earth in cable harness for the gas valve Gas valve defective (coils shorted to earth). Electronic defective |
| F.62 | Fault: Gas valve switch-off delay – Delayed shutdown of gas valve. Delayed extinguishing of flame signal. Gas valve leaking Electronics defective |
| F.63 | EEPROM error – Electronics defective |
| F.64 | Electronics/NTC fault – Supply or return NTC short circuited, electronics defective |
| F.65 | Electronic temperature fault – Electronics overheating due to external influences, electronics defective |
| F.67 | Electronics/flame fault – Implausible flame signal, electronics defective |
| F.68 | Unstable flame signal fault – Air in gas, gas flow pressure too low, wrong air ratio, condensate route blocked, wrong gas restrictor, ionisation flow interruption (cables, electrodes), flue gas recirculation, condensate route |
| F.70 | Invalid device specific number (DSN)- Spare part case: Display and PCB replaced at same time and DSN not set, wrong or missing output range coding resistor |
| F.71 | Flow NTC fault – Flow temperature sensor signalling constant value: Flow temperature sensor incorrectly positioned at supply pipe. Flow temperature sensor defective |
| F.72 | Flow/return NTC fault – Flow/return NTC temperature difference too great → flow and/or return temperature sensor defective |
| F.73 | Water pressure sensor signal in the wrong range (too low) – Interruption/short circuit of water pressure sensor, interruption/short circuit to GND in supply line to water pressure sensor or water pressure sensor defective |
| F.74 | Water pressure sensor signal outside correct range (too low) – Cable to water pressure sensor has short-circuited at 5V/24 V or internal fault in water pressure sensor |
| F.75 | Fault, no pressure change detection when starting pump – Water pressure sensor and/or pump defective, air in heating installation, too low water pressure in boiler; check adjustable bypass, connect external expansion vessel to return |
| F.76 | Overheating protection on primary heat exchanger has responded – Cable or cable connections for safety fuse in primary heat exchanger or primary heat exchanger defective |
| F.77 | Flue non-return flap/condensate pump fault No response from flue non-return flap or condensate pump defective |
| F.78 | Interruption to DHW outlet sensor at external controller -UK link box is connected, but hot water NTC not bridged |
| F.83 | Flow and/or return temperature sensor temperature change fault – When the burner starts, the temperature change registered at flow and/or return temperature sensor is non-existent or too small. Not enough water in the boiler. Flow and/or return temperature sensor not in correct position at pipe |
| F.84 | Fault: Flow/return temperature sensor difference implausible – Flow and return temperature sensors return implausible values. Flow and return temperature sensors have been inverted. Flow and return temperature sensors have not been correctly fitted |
| F.85 | Fault: Flow and return temperature sensors incorrectly fitted- Flow and/or return temperature sensors have been fitted to the same pipe/wrong pipe |
| F.92 | Coding resistor fault- The coding resistor on the PCB does not match the entered gas family. Check the resistor, repeat the gas family check and enter the correct gas family. |
| F.93 | Gas group fault- Combustion quality outside the permitted range: Wrong gas restrictor, recirculation, wrong gas family, internal pressure measuring point in venturi blocked (do not use lubricant on O-ring in venturi.). Gas family check prematurely terminated. |
It’s important to note that these codes may vary depending on the specific model of Vaillant boiler you have. Always refer to your boiler’s user manual or contact a qualified heating engineer if you are unsure about any error codes on your boiler.