3A High

Keston 3A Fault Code

The Keston 3A fault code means: your boiler has detected an issue with its internal electrical protection system, meaning it has shut down to prevent potential damage to its electronic components.. It appears on 1 Keston model 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: Internal fuse rating
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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Keston models that show the 3A fault code

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

Source

Keston 3A fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.

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