F43 High
Your boiler has stopped to prevent overheating because it cannot move water through the system properly or there is an air pocket trapped inside.
Technical description: Exchanger protection intervention – could be because no system water circulation or there’s air in the system
Typical repair cost: £100-280 (including labour)
DIY fix possible
Check the central heating pressure gauge is between 1 and 1.5 barBleed all radiators to remove trapped airTry resetting the boiler using the 'R' button
Protect yourself from future repair bills
A boiler cover plan would cover faults like F43 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulating pump
- Automatic air vent
- System pressure sensor
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