BoilerTroubleshooting2026-02-26
Combi Diverter Valve Stuck: Symptoms
A stuck diverter valve causes heating or hot-water faults depending on its position.
The diverter valve directs the combi between heating and hot water; when stuck, one fails.
Symptoms
Stuck in heating: no hot water. Stuck in hot water: no heating, or radiators warm only when a tap runs.
The fix
A technician frees or replaces the diverter valve and tests both heating and hot-water modes.
Key takeaways
- Stuck = heating or hot-water fault
- Radiators warm only on tap = classic sign
- Internal part — needs a technician
- Repair or replace the valve
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