How much does it cost to fix Grant error code RED blinking (0.5s)?

Typical repair cost for the Grant RED blinking (0.5s) fault is £150-300 including labour.

RED blinking (0.5s) High

Grant RED blinking (0.5s) Fault Code

Q: What does the Grant RED blinking (0.5s) fault code mean?

Your boiler has detected a signal that it is already burning fuel even though it has not been told to start, so it has safely shut itself down to prevent an unsafe situation.

Also written as REDBLINKING05S — same fault.

The Grant RED blinking (0.5s) fault code means: your boiler has detected a signal that it is already burning fuel even though it has not been told to start, so it has safely shut itself down to prevent an unsafe situation.. It appears on 5 Grant models in our database.

Technical description: Lockout for false flame signal

Typical repair cost £150-300 (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 RED blinking (0.5s) fault code

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

Source

Grant RED blinking (0.5s) 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