High
DHW PUMP indicator Fast flash on Grant Vortex Pro 15-26

Your boiler is struggling to accurately measure the temperature of the water inside its internal storage tank, which means it may fail to provide hot 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.

What the manual says

Manufacturer manual

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

From this model's manual
Verified against the Grant Vortex Pro Internal Combi Installation Servicing Instructions DOC88 Rev00 May 2012 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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