High Lockout
E164 on Potterton Promax

Your boiler has detected a problem with the sensor that monitors your hot water temperature or a switch that controls water flow, which usually means your hot water will stop working properly.

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

Domestic hot water sensor error – could be a heating flow switch error)

What causes this fault?

This fault occurs when the boiler's control board receives a signal that is outside of the normal range from the hot water temperature sensor or the flow switch. This is usually caused by the internal electrical components wearing out over time or a loose connection in the wiring that prevents the boiler from accurately monitoring the water temperature.

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.

Find a Gas Safe engineer
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Related fault codes

E110View →E160View →E161View →

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