E14
Heatmiser
Relay Output Fault
Thermostat shows E14 and heating output is stuck on or off
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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
Welded relay contacts due to overload, Incorrect load type connected (e.g., motorised valve exceeding rating), PCB track damage, Internal relay coil failure
How to Fix / Troubleshooting
Safety first: Turn off power at the consumer unit. Verify with a voltage tester before touching any wiring.
Steps:
- Check the load rating of the thermostat relay (e.g., 3A) and compare with the connected load (valves, pumps). If the load exceeds the rating, rewire via a suitable contactor or wiring centre.
- Inspect the wiring at the thermostat output terminals (e.g., NO/COM) for signs of overheating or burning.
- Disconnect the load wire and test the relay operation by calling for heat and measuring continuity across the relay contacts with a multimeter.
- If the relay is stuck closed or open regardless of demand, the thermostat PCB is faulty and must be replaced.
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Repair Difficulty
Hard
4/5
Required Part
Heatmiser Smart Thermostat Main PCB
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