F43 High
Your boiler has shut down to prevent the heat exchanger from overheating, often because the water isn't flowing through the system correctly.
Technical description: Exchanger protection intervention
Typical repair cost: £120-£450 (including labour)
DIY fix possible
Check that your home heating system pressure is between 1.0 and 1.5 barEnsure all radiator valves and isolation valves are fully openTry resetting the boiler using the 'R' button once the unit has cooled down
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
- Central heating pump
- Heat exchanger (descaling)
- Temperature sensor (NTC thermistor)
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