BoilerTroubleshooting2026-02-26
Hot Water Works but Heating Doesn't
This classic combi fault usually traces to the diverter valve, pump or thermostat.
If hot water flows but radiators stay cold, the heating circuit isn't getting flow.
Common causes
A diverter valve stuck in hot-water position, a seized pump, a thermostat fault, or low pressure prevent the heating circuit from running.
What to do
Confirm the thermostat calls for heat and pressure is correct; the diverter valve or pump likely needs a technician.
Key takeaways
- Diverter valve is a common cause
- Check thermostat and pressure
- A seized pump stops heating
- Needs a technician for internal parts
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