Fast flash High

Grant Fast flash Fault Code

Also written as FASTFLASH — same fault.

The Grant Fast flash fault code means: your boiler has failed to light the burner and is currently locked out to prevent any issues.. 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: Burner indicator flashing fast (Refer to Section 12.2 (C))
Typical repair cost £120-250 (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 Fast flash fault code

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

Source

Grant 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