D4 341 High
Your boiler is overheating because water is not moving through the system quickly enough to carry the heat away.
Technical description: Primary flow temperature rising too fast
Typical repair cost: £150-£450 (including labour)
DIY fix possible
Ensure all radiator valves (TRVs) are turned to their highest settingCheck that the boiler pressure is between 1 and 1.5 bar on the gaugeSwitch the electricity to the boiler off and back on again to reset the system
Protect yourself from future repair bills
A boiler cover plan would cover faults like D4 341 — no call-out fees, no surprises.
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Parts commonly replaced
- Central heating pump
- Main heat exchanger (flushing/cleaning)
- Flow temperature sensor
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