How much does it cost to fix Grant error code Green/Red flashing?

Typical repair cost for the Grant Green/Red flashing fault is £120-250 including labour.

Green/Red flashing High

Grant Green/Red flashing Fault Code

Q: What does the Grant Green/Red flashing fault code mean?

Your boiler has detected light inside the combustion chamber when it should be dark, causing it to lock itself out as a safety precaution.

Also written as GREENREDFLASHING — same fault.

The Grant Green/Red flashing fault code means: your boiler has detected light inside the combustion chamber when it should be dark, causing it to lock itself out as a safety precaution.. It appears on 5 Grant models in our database.

Technical description: Burner lockout occurs if extraneous light or flame is detected for 25 seconds during pre-purge

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 Green/Red flashing fault code

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

Source

Grant Green/Red flashing 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 27 April 2026