Immergas
Unwanted Heating / Control Fault
Boiler heats radiators even when there is no call for heating (overheating house).
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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
Stuck diverter valve allowing flow to CH, Room thermostat contacts stuck closed, PCB relay stuck on CH demand, Incorrect wiring links
How to Fix / Troubleshooting
Safety: Radiators may become very hot; use caution.
- Check room thermostat: Turn the thermostat down or off and see if the boiler stops firing. If not, the thermostat or its receiver (wireless) may be stuck on and should be replaced.
- Wiring check (engineer): Verify that external controls are wired correctly and that no permanent link is forcing CH demand.
- Diverter valve: If the boiler fires mainly for DHW but radiators heat up at the same time, the diverter valve may be leaking internally and should be replaced.
- PCB relay: If CH output remains on with no demand, the PCB relay may be stuck and require PCB replacement.
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Repair Difficulty
Hard
4/5
Required Part
Diverter Valve Assembly
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