E40 High
Your boiler has detected an issue with the sensor that monitors the temperature of the water coming back from your radiators, preventing the system from running efficiently or at all.
Technical description: Central heating return thermistor fault
Typical repair cost: £100-£180 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Protect yourself from future repair bills
A boiler cover plan would cover faults like E40 — no call-out fees, no surprises.
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Parts commonly replaced
- Central heating return NTC thermistor
- Connecting wiring harness
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