F43 High
Your boiler has stopped working because water is not moving through it properly or there is trapped air causing it to overheat.
Technical description: Exchanger protection activation – no system circulation air in system
Typical repair cost: £100-£350 (including labour)
DIY fix possible
Check that your system pressure is between 1 and 1.5 bar on the pressure gaugeBleed all radiators in your home to remove trapped airEnsure all radiator valves and external isolation valves are fully open
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
- Circulation Pump
- Automatic Air Vent
- Main Heat Exchanger
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