594 Emergency

Grant 594 Fault Code

The Grant 594 fault code means: your boiler is struggling to get the necessary amount of air for safe combustion because the external ventilation opening is likely blocked or obstructed.. It appears on 6 Grant models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: Vent E (cm²)
Typical repair cost £100-200 (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 594 fault code

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

Source

Grant 594 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