EHC
Heating Circuit Isolation / Diverter Fault
Boiler produces hot water but central heating does not work.
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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 in DHW position, Faulty motorised zone valve, Heating controls not calling for heat, Airlock in heating circuit
How to Fix / Troubleshooting
Safety: Pipework may be hot; use caution when touching valves.
User checks:
- Ensure the heating is switched on at the programmer and thermostat is turned up.
- Check radiator valves are open.
Engineer checks:
- On EHC combi boilers, test the diverter valve operation; replace the cartridge or actuator if stuck.
- On system/regular boilers, check motorised zone valves for correct operation and end-switch function.
- Bleed air from the heating circuit and pump.
Once the diverter or zone valve is operating correctly, heating should resume while hot water remains available.
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Repair Difficulty
Medium
3/5
Required Part
Diverter Valve Assembly
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