High
E40 on Baxi Profile

Your boiler has lost its ability to accurately measure the temperature of the water coming back from your radiators, usually because a sensor has failed or its wiring is damaged.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Central heating return negative temperature coefficient (NTC) thermostat fault.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

E20View →E28View →E50View →

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