How much does it cost to fix British Gas error code AC?

Typical repair cost for the British Gas AC fault is £120-350 including labour.

AC High

British Gas AC Fault Code

Q: What does the British Gas AC fault code mean?

Your boiler's internal computer is having trouble communicating with an optional accessory or plug-in module, which is preventing the system from working correctly.

The British Gas AC fault code means: your boiler's internal computer is having trouble communicating with an optional accessory or plug-in module, which is preventing the system from working correctly.. It appears on 2 British Gas models in our database.

Technical description: Module not detected.

Typical repair cost £120-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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British Gas models that show the AC fault code

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

Source

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

British Gas RD 542i Combi manual (PDF)

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026