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If you have an issue with your Vaillant boiler why not check out the possible causes. We have created a list of fault codes and possible causes below. If you still require help we carry out boiler repairs and breakdowns in the poole and Bournemouth Area .

For Boiler Breakdowns in Bournemouth Call 01202 481000

For Boiler Breakdowns in Poole Call 01202 668822

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  • 00 – Flow Temperature Sensor interruption – Usually this means that the NTC plug has come loose, or it’s damaged in some way
  • 01 – Return Temperature Sensor interruption – Usually this means that the NTC plug has come unstock or has been severely damaged, or that the NTC is damaged
  • 10 – Flow NTC short circuit – Typically implies that the NTC is damaged, or that there is a short circuit in the cable harness
  • 11 – Return NTC short circuit – Usually means that the NTC has been compromised, or that a short circuit has occurred in the cable harness
  • 20 – Safety Switch off temperature limiter – Usually means there is an incorrect “Earth” connection between the cable harness and the boiler
  • 22 – Safety Switch off low water pressure – There will be no water pressure, or the pressure is too low in the boiler – additionally, it could be a damaged sensor
  • 23 – Safety Switch off with high temperature rise – Usually means that the bump has become blocked, or there is a poor output from the pump. Could also mean air in the boiler
  • 24 – Safety Switch off fast temperature rise – Usually implies a break in the plug connection, or a break in the cable harness
  • 25 – Safety Switch off flue gas temperature risen – The pump could be blocked or not performing to it’s capacity, or there could be a break in the cable harness
  • 26 – Gas Valve with no function – Usually implies that the gas stepper motor has become disconnected or there is an interruption in the cable harness
  • 27 – Safety Switch off flame simulations – Points to moisture on electronics, or a damaged flames sensor, or a leaking gas valve
  • 28 – Failure to startup, unsuccessful ignition – Defective gas meter or the gas pressure regulator has been triggered. Could also be that air has got into the gas supply, or the gas pressure is too low
  • 29 – Failure to startup, failed ignition – The could supply cold have dropped, there could be a condensate duct blocked or there is a faulty earthing in the boiler
  • 32 0 Fan Fault – The plug could not be inserted properly, or there could be a snap in the cable harness
  • 49 – eBUs Fault – Short circuit on the eBUS, or an overload of the two power supplies within the eBUS
  • 61 – Gas valve regulation – Usually defective electrics or damaged gas valve, but it could be a short-circuit to the earth in a cable harness
  • 62 – Gas valve switch-off delay – Could be a delayed shutdown of the gas valve, a leaking gas valve or defective electrics
  • 63 – EEPROM – This can only be caused by defective electrics
  • 64 – NTC Fault – Caused by damage to the supply and return of the NTC or defective electrics
  • 65 – Electronics temperature fault – Usually caused by overheating due to other influences or defective electronics
  • 67 – Flame Fault – A damaged flame signal, or faulty electronics
  • 68 – Unstable flame signal – There usually could be air in the gas, or too low a flow pressure
  • 70 – Invalid DSN (Device Specific Number) – The display and PCB were changed at the same time, and the appliance code needs reset
  • 71 – Flow NTC Fault – A problem with the flow temperature sensor or a defective sensor
  • 72 – Flow/Return NTC Fault – Flow/return NTC temperature difference which is too high, or the sensor could be damaged
  • 73 – Water pressure sensor signal too low – Short-circuit to the water pressure sensor, or damage to the supply line to the water pressure
  • 74 – Water pressure sensor signal too high – The cable to the water pressure may be damaged, or there is damage inside with the pressure sensor
  • 75 – No pressure change detection – Usually damage to the pump or the water pressure sensor, or there is air in the heating installation
  • 76 – Overheating protection responding – Usually means that the safety fuse cables have become damaged and need replaced
  • 77 – Flue non-return flap/condensate pump damage – When there is no response from the flap, could be caused by defective condensate pump
  • 78 – DWH Outlet Sensor fault – Usually means that the UK link box is connected, but there is no bridge between the NTC and the hot water
  • 83 – Return temperature sensor change fault – When the burner begins, the temperature registered may be non-existent or undervalued. Usually caused by a lack of water in the boiler
  • 84 – Implausible temperature difference with flow/return sensor – Usually caused by an inversion of the flow and return sensors, or that they been wrongly fitted
  • 85 – Incorrect fitting of Fault: Flow and return sensors – Sensors have been fitted to the same pipe or the wrong pipes