F.26
Vaillant
Gas Valve Regulation Fault / Gas Valve Drive Error
F.26 displayed, boiler does not ignite, gas valve does not click
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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
Defective gas valve coil, Loose gas valve connector, Faulty gas valve modulation control from PCB, Incorrect gas valve calibration
How to Fix / Troubleshooting
Safety: Gas components must only be serviced by qualified personnel. Turn off gas and power.
Basic user check:
- Confirm that the external gas supply to the boiler is on and that other gas appliances (if present) work.
Professional checks:
- Verify correct voltage is supplied to the gas valve during ignition.
- Check gas valve coil resistance and replace the gas valve if out of specification.
- Inspect and reseat the gas valve electrical connector.
- Perform combustion analysis and adjust or calibrate the gas valve according to Vaillant procedures after replacement.
Do not attempt to open or adjust the gas valve yourself.
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Repair Difficulty
Professional Required
5/5
Required Part
Gas Valve Assembly
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