FAULTNEST FAULT CODES
Vaillant Boilers & Heating Fault Codes
Browse Vaillant boilers & heating fault and error codes, meanings, likely causes and diagnostic checks.
AVAILABLE CODES
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16 published codes currently listed for this manufacturer and category.
Flow temperature sensor fault
The flow temperature sensor circuit is interrupted or the sensor signal is unavailable.
Return temperature sensor fault
The return temperature sensor circuit is interrupted or the sensor signal is unavailable.
Safety switch-off: overheating temperature reached
The boiler has shut down because an overheating safety threshold has been reached.
Low water pressure in the system
Vaillant F.22 indicates low system water pressure or a related water-pressure/circulation issue.
Flow and return temperature spread too great
The boiler has detected an excessive temperature difference between flow and return.
Temperature rises too quickly
The boiler has detected an abnormally rapid increase in water temperature.
Flue gas temperature too high
The boiler has detected an excessive flue-gas temperature condition.
Flame signal detected while burner is off
The boiler control has detected a flame signal when the burner should not be operating.
Flame signal not detected during ignition
F.28 means the boiler did not detect a flame signal during the ignition phase.
Ignition unsuccessful after flame loss
F.29 means the flame was lost during operation and the subsequent ignition attempt was unsuccessful.
Fan fault
The boiler has detected a fault associated with the combustion fan system.
eBUS voltage too low
The boiler has detected an eBUS communication voltage fault.
Gas valve control system fault
The boiler control cannot correctly actuate the gas valve.
Electronics / temperature sensor fault
The boiler has detected an electronics or NTC sensor/analogue-conversion fault.
Unstable flame fault
The boiler has detected an unstable flame or implausible analogue flame signal.
Pressure change too low when pump starts
The boiler does not detect the expected pressure response when the pump starts.
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