High
CH PUMP indicator Fast flash on Grant Vortex 15-20

Your boiler's temperature sensor is failing to communicate properly, which is preventing it from heating your water correctly.

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

Fast flash (twice per second): Indicates a possible fault with the ‘Flow’ thermistor. Check CH ‘Flow‘ thermistor connection to PCB. Replace ‘Flow’ thermistor.

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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CH PUMP slow flashView →

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