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Worcester Bosch AC Fault Code

The Worcester Bosch AC fault code means: your boiler's internal computer is having trouble communicating with one of its main control parts, meaning the system cannot run.. It appears on 22 Worcester Bosch models 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: Module not detected.

What causes the Worcester Bosch AC fault?

This fault occurs when the boiler's central brain loses its physical connection with one of the primary control modules, preventing it from sending or receiving instructions. The most common reason is an electrical failure within the main circuit board or a loose internal wired connection that has deteriorated over time due to heat and vibration. Because the system can no longer verify that all safety components are connected, it shuts down immediately to prevent damage.

Typical repair cost £180-£450 (including labour)

Engineer required

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

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Worcester Bosch models that show the AC fault code

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

Source

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

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026