Boiler shows flame present when there should be none, or fails to start due to false flame detection

Safety: Isolate power and fuel. Do not attempt to run the boiler with suspected electrical faults.

• Inspect ionisation electrode: Remove and clean the electrode. Ensure the ceramic insulator is intact and that the metal rod is not touching the burner head or other metal parts.
• Check cable routing: Ensure the ionisation lead is not damaged or rubbing on sharp edges. Replace if insulation is compromised.
• Dry moisture: If there is condensation or water inside the burner compartment, dry thoroughly and identify the source of ingress.
• Earth connection: Verify that the boiler and burner are properly earthed. Loose earth connections can cause erratic flame detection.
• Professional diagnosis: If the issue persists, a technician should test the burner control box and replace it if necessary.