Junkers
DHW Priority / Diverter Valve Fault
Furnace provides heating but no domestic hot water
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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 on Junkers combi, Faulty DHW flow sensor, Diverter motor failure, Blocked DHW plate heat exchanger
How to Fix / Troubleshooting
Safety first: Isolate power and water before working on the hydraulic block.
- 1. Check DHW demand: Open a hot tap fully and observe if the boiler recognises demand (DHW symbol on display, if available).
- 2. Flow sensor: If no DHW demand is indicated, inspect and clean/replace the DHW flow sensor or turbine.
- 3. Diverter valve operation: Listen for the diverter motor moving when switching between heating and DHW. If silent or stuck, remove and inspect the valve. Clean or replace the cartridge and/or motor.
- 4. Plate heat exchanger: If the boiler fires for DHW but water remains cold, the plate heat exchanger may be blocked and should be descaled or replaced.
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Repair Difficulty
Hard
4/5
Required Part
Three-Way / Diverter Valve
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