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

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