Immergas
Heating Demand / Diverter Valve Fault
Boiler provides hot water but central heating does not come on, even when room thermostat calls for heat.
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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
Faulty room thermostat or wiring, Stuck diverter valve, Faulty diverter motor, PCB not recognising CH demand
How to Fix / Troubleshooting
Safety: Isolate power before working on control wiring or internal valves.
- Check controls: Ensure the room thermostat or Immergas controller is set to heating mode and above room temperature. Replace batteries if wireless.
- Bypass test (engineer): Temporarily link the room thermostat terminals at the boiler to confirm that the boiler responds to a direct CH demand.
- Diverter valve observation: During a CH demand, observe whether the diverter motor moves. If not, test and replace the motor or complete valve assembly.
- PCB input: If the boiler does not recognise CH demand even with a link, the PCB may be faulty.
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Repair Difficulty
Hard
4/5
Required Part
Diverter Valve Assembly
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