High
A8 362 on Worcester Bosch Heatslave

Your boiler is struggling to operate because the electrical power supply to it is unstable or too low, or there is a communication issue with its control chip.

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

Low mains voltage – the voltage may be interrupted, inconsistent or heat control module (HCM) invalid

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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