E03
Heatmiser
Internal Air Sensor Fault
Thermostat displays E03 and shows no room temperature, heating output disabled
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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
Failed internal NTC sensor on PCB, Dry solder joint on sensor pins, Liquid ingress into thermostat, Overheating damage to main PCB
How to Fix / Troubleshooting
Safety first: Isolate power before removing the thermostat from the wall.
Steps:
- Remove the thermostat from the wall plate and visually inspect the PCB for signs of burning, corrosion, or moisture.
- Check that the thermostat has not been installed directly above a radiator or in direct sunlight, which can overheat the internal sensor.
- If the model supports an external room sensor, connect a compatible Heatmiser remote air sensor to the designated terminals and change the sensor mode in the installer settings to use the remote sensor instead of the internal one.
- If no external sensor option exists or E03 persists, the internal sensor or PCB is defective and the thermostat will typically need to be replaced.
Warning: Do not attempt to re-solder or modify the PCB unless you are a qualified electronics technician; this can create a fire or shock hazard.
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Repair Difficulty
Hard
4/5
Required Part
Heatmiser Smart Thermostat Main PCB
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