F23 High
Your boiler has sensed that water is not moving through the system properly, which is causing it to shut down to prevent overheating.
Technical description: Water circulation fault
Typical repair cost: £150-350 (including labour)
DIY fix possible
Check that the boiler pressure is between 1 and 1.5 bar on the displayEnsure all radiator valves are fully openListen for air in the system and bleed radiators if necessary
Protect yourself from future repair bills
A boiler cover plan would cover faults like F23 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulation pump
- Temperature thermistors (NTC sensors)
- Main heat exchanger (de-scaling)
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