High
CH PUMP Fast flash on Grant Vortex 15-20

Your boiler's temperature sensor is disconnected or faulty, meaning it cannot accurately track the heat of the water and has stopped your heating from working.

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

Check CH ‘flow’ thermistor connection to the 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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