High Lockout
E41 on Potterton Powermax HE

Your boiler has stopped working because one of its internal temperature sensors has developed an electrical fault and can no longer send information to the main control board.

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

Return sensor short circuit. Check cable/connections not damaged. Renew sensor/cable. Check connections on control

What causes this fault?

This fault occurs when the electrical resistance in the return temperature sensor drops to a level that indicates a short circuit, meaning the boiler can no longer monitor the water temperature accurately. The most common reason is internal failure of the sensor's thermistor component, but it can also be caused by water damage or heat degradation affecting the wiring harness.

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

E40View →E42View →

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