Thermona
No Power / Internal Fuse or PCB Failure
Boiler display is blank, no lights or response, but mains supply appears present.
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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
Blown internal fuse on Thermona PCB, Faulty main on/off switch, Loose live/neutral connection at terminal block, Failed PCB power supply section
How to Fix / Troubleshooting
Safety: Isolate the boiler before removing the front cover. Electrical work must comply with local regulations.
- Check external power: Verify the circuit breaker or fused spur is ON and the fuse is intact. Test the socket or spur with another appliance if possible.
- Inspect terminal block: Remove the front cover and check that live, neutral, and earth are securely connected at the Thermona terminal block.
- Internal fuse (engineer level): A technician can check and replace the internal PCB fuse with the correct rating if blown, and investigate the cause.
- PCB replacement: If the power supply section of the PCB has failed, the main control board will need replacement.
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Repair Difficulty
Hard
4/5
Required Part
Main Control PCB
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