J6-01 High
Your boiler is getting too hot too quickly because water isn't flowing through the system properly or the pressure has dropped too low.
Technical description: Flow temperature sensor overheating due to a blocking fault or a lockout error – the valves of the radiator heating circuit may have an issue or the water pressure is low and needs filling
Typical repair cost: £100-£250 (including labour)
DIY fix possible
Check the pressure gauge and top up the water to 1.5 bar if it is lowEnsure at least two or three radiator valves (TRVs) are fully openRestart the boiler to see if the error clears
Protect yourself from future repair bills
A boiler cover plan would cover faults like J6-01 — no call-out fees, no surprises.
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Parts commonly replaced
- Flow Temperature Sensor (NTC)
- Circulation Pump
- External Filling Loop
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