F.62
Vaillant
Delayed Gas Valve Closure / Gas Valve Sticking
F.62 gas valve closing fault; appliance may continue burning briefly after demand ends or lock out
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Sticking gas valve mechanism, Contaminated gas valve, Faulty PCB control of gas valve, Wiring fault causing valve to remain energised
How to Fix / Troubleshooting
Safety: This is a serious gas safety fault. Immediately switch off the appliance and isolate the gas supply. Only a qualified gas engineer must proceed.
- Do not attempt to free the valve: Gas valves must not be dismantled or lubricated. If sticking is suspected, the valve must be replaced.
- Check wiring and PCB: Verify that the gas valve is de-energised when there is no demand. If voltage remains present, the PCB or wiring is faulty.
- Replace gas valve: Fit a new Vaillant-approved gas valve and perform all required leak and combustion checks.
- Replace PCB if needed: If the PCB is holding the valve open incorrectly, replace the PCB and retest.
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Repair Difficulty
Professional Required
5/5
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