AC High

Worcester Bosch AC Fault Code

The Worcester Bosch AC fault code means: your boiler has lost communication between its internal computer and a key electrical sensor or motor, meaning it cannot operate safely.. It appears on 17 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: No electrical connection between component and PCB

What causes the Worcester Bosch AC fault?

This fault occurs when the boiler's main control board loses its electrical link with a vital internal component, such as a sensor or the fan motor. It is usually caused by a loose connection, a damaged wiring harness, or a failure within the circuit board itself, preventing the boiler from sending or receiving signals. Because the system can no longer monitor safety or performance, it shuts down to prevent damage.

Typical repair cost £120-450 (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 31 August 2026