High Lockout
E83484 on Potterton Powermax HE

Your boiler is struggling to accurately measure the temperature of your hot water, which usually means your taps will only run cold.

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

DHW NTC Sensor c/w cable 1.25 m

What causes this fault?

This fault occurs when the internal sensor responsible for monitoring your hot water temperature fails or sends an unreadable signal to the main control board. The most common reason is that the sensor has physically degraded over time or a loose connection in the wiring harness is preventing the boiler from knowing how hot the water is. To prevent overheating, the boiler will stop heating your water entirely until the part is replaced.

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

A03View →

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