Heatmiser
No Power to Thermostat
Thermostat display completely dead, no lights or response
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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 fuse in fused spur, Tripped MCB, Loose live/neutral at thermostat, Failed Heatmiser 12V PSU (for low-voltage models)
How to Fix / Troubleshooting
Safety first: Turn off the circuit at the consumer unit before removing the thermostat or spur cover.
Steps:
- Check the fused spur feeding the heating controls; replace the fuse (typically 3A) if blown, and investigate why it blew (short circuit, overload).
- Verify that the relevant MCB or RCD in the consumer unit has not tripped; reset if necessary.
- Remove the thermostat from the wall and check that Live and Neutral are present and firmly connected. Use a multimeter or approved voltage tester.
- On 12V systems, measure the output of the Heatmiser 12V power supply at the wiring centre; replace the PSU if no voltage is present.
- If correct voltage is present at the thermostat but it remains dead, the thermostat PCB is likely failed and should be replaced.
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Repair Difficulty
Medium
3/5
Required Part
Heatmiser 12V Power Supply
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