F26
Protherm
Gas Valve Control / Internal Error
F26 displayed, appliance may not modulate correctly or may shut down
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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
Internal gas valve fault, Incorrect gas valve type fitted, Wiring error after service, PCB output fault
How to Fix / Troubleshooting
Safety first: Isolate gas and power. Only licensed gas technicians should work on gas valves.
- Verify correct valve: Confirm that the installed gas valve matches the Protherm part number and gas type.
- Inspect wiring: Check all gas valve connectors for correct placement and secure fit.
- Measure control signal: A technician should verify that the PCB is sending the correct control signal to the valve.
- Replace gas valve: If the valve does not respond correctly, replace it and perform full combustion setup.
- Replace PCB if needed: If a known-good valve still triggers F26, replace the main PCB.
Warning: After any gas valve or PCB replacement, perform leak tests and combustion analysis.
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Repair Difficulty
Professional Required
5/5
Required Part
Gas Valve Assembly
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