45 High
Your boiler is overheating because the water is not flowing through the system as quickly as it should.
Technical description: High-temperature difference
Typical repair cost: £120-£350 (including labour)
DIY fix possible
Check that all radiator valves (TRVs) are fully openEnsure the external system pump is running and hasn't seizedCheck for any blockages in the system filters
Protect yourself from future repair bills
A boiler cover plan would cover faults like 45 — no call-out fees, no surprises.
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Parts commonly replaced
- External Central Heating Pump
- Flow/Return Thermistor
- Heat Exchanger (if scaled)
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