Vaillant Fault Codes

Comprehensive reference table of all Vaillant boiler error codes. Click any code for detailed troubleshooting steps.

Pro Tip

Check your boiler's digital display panel (usually behind a drop-down cover) to find the current active fault code.

Error CodeDescription
F.22Safety switch-off: Water pressure is too low or system is entirely devoid of water.
F.28Boiler ignition fault: Unsuccessful ignition when starting up; check gas supply.
F.29Flame loss fault: Flame extinguishes during operation; possible gas interruption.
F.75Pressure sensor fault: Insufficient pressure jump detected when pump starts.
F.23Safety switch-off: Temperature spread between flow and return is too great.
F.24Safety switch-off: Temperature increased too quickly; dry fire or airlock detected.
F.27False flame detection: Monitoring electrode reports an incorrect flame.
F.32Fan fault: Fan speed outside tolerance values or fan frost protection active.
F.61Gas valve fault: The gas valve assembly cannot be actuated electrically.
F.62Gas valve error: Delayed switch-off sequence for the gas valve after flame is extinguished.
F.00 / F.0Flow temperature sensor is defective, disconnected, or interrupted.
F.01 / F.1Return temperature sensor is defective, disconnected, or interrupted.
F.10Flow temperature sensor is defective or actively short-circuiting.
F.11Return temperature sensor is defective or actively short-circuiting.
F.20Safety shutdown: Maximum overheating temperature has been reached at the NTC.
F.25Safety switch-off: The flue gas temperature is too high.
F.26Gas valve assembly stepper motor is defective or not connected.
F.49Undervoltage detected on the eBus communication circuit.
F.63EEPROM is faulty; internal control board memory error.
F.64Defect with the electronics, safety-relevant sensor, or analogue-to-digital converter.
F.65Electronics temperature is too high; external heat source or electrical fault.
F.67Flame signal is weak or not detected by the ASIC.
F.70Invalid product code (Device Specific Number) or incorrect coding resistor.
F.71Flow temperature sensor returns implausible or incorrect values.
F.72Deviation in the water pressure sensor or return temperature sensor.
F.73Water pressure sensor is not connected or has short-circuited.
F.76Safety cut-out in the primary heat exchanger is defective; major overheating.
F.83Dry fire detected; flow sensor temperature rise is too quick relative to burner output.
F.84Permanent temperature difference between flow and return NTC thermistors.
F.92Combustion fault; the coding resistor does not match the entered gas group.
F.93Combustion regulation fault; gas/air mixture is outside the permitted range.

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