How much does it cost to fix Worcester Bosch error code 6a?

Typical repair cost for the Worcester Bosch 6a fault is £120-£350 including labour.

6a High

Worcester Bosch 6a Fault Code

Q: What does the Worcester Bosch 6a fault code mean?

Your boiler has detected that the exhaust gases are getting too hot and has shut down as a safety precaution to prevent damage.

Also written as 6A — same fault.

The Worcester Bosch 6a fault code means: your boiler has detected that the exhaust gases are getting too hot and has shut down as a safety precaution to prevent damage.. It appears on 5 Worcester Bosch models in our database.

Technical description: Type a Flue overheat thermostat (Screw thread)

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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Worcester Bosch models that show the 6a fault code

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

Source

Worcester Bosch 6a 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