DHW PUMP indicator Fast flash High

Grant DHW PUMP indicator Fast flash Fault Code

Also written as DHWPUMPINDICATORFASTFLASH — same fault.

The Grant DHW PUMP indicator Fast flash fault code means: 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.. It appears on 6 Grant models in our database.

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 ‘Store’ thermistor. Check DHW ‘Store’ thermistor connection to PCB. Replace ‘Store’ thermistor.
Typical repair cost £120-220 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Grant models that show the DHW PUMP indicator Fast flash fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Grant DHW PUMP indicator Fast flash fault code information on this page is sourced and cross-checked against the official Grant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026