F15
Glow-worm
Gas Valve Control Fault
Boiler displays F15; the pump may run, but the burner does not ignite.
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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
Gas valve coil open/short circuit, Wiring fault between the PCB and gas valve, PCB output stage failure, Incorrect gas valve fitted
How to Fix / Troubleshooting
Safety: Turn off the power and isolate the gas supply before any work on the gas valve. Only Gas Safe registered engineers may work on gas components.
- Reset and observe: Reset the boiler and listen for fan operation. If the fan runs but there is no ignition attempt and F15 appears, the gas valve may not be energized.
- Engineer tasks:
- Measure the gas valve coil resistance and compare it to the specification.
- Check the wiring harness from the PCB to the gas valve for continuity and secure connections.
- Verify that the PCB is sending the correct voltage to the gas valve on ignition demand.
- Replace the gas valve or PCB as indicated by diagnostic tests.
Do not attempt to adjust or replace the gas valve yourself; incorrect setup can be dangerous.
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Repair Difficulty
Professional Required
5/5
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