345 High

Worcester Bosch 345 Fault Code

The Worcester Bosch 345 fault code means: your boiler is failing to detect any heat being produced after the burner lights, which suggests the internal water circulation has stopped or the temperature sensors are not working correctly.. It appears on 4 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: EF Supply and/or return temperatures do not change after burner start
Typical repair cost £150-300 (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 345 fault code

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

Source

Worcester Bosch 345 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 7 July 2026