How much does it cost to fix Worcester Bosch error code 1-A5?

Typical repair cost for the Worcester Bosch 1-A5 fault is £120-£280 including labour.

1-A5 High

Worcester Bosch 1-A5 Fault Code

Q: What does the Worcester Bosch 1-A5 fault code mean?

Your boiler has detected that the internal water temperature is higher than it should be, causing the system to shut down to prevent damage.

Also written as 1A5 — same fault.

The Worcester Bosch 1-A5 fault code means: your boiler has detected that the internal water temperature is higher than it should be, causing the system to shut down to prevent damage.. It appears on 1 Worcester Bosch model in our database.

Technical description: Actual temperature: Flow temperature at the flow temperature sensor.

What causes the Worcester Bosch 1-A5 fault?

This fault occurs when the water leaving the boiler exceeds its safe temperature limit, causing the system to shut down for safety. The most common reasons are a blockage in the pipework, a pump that has failed to circulate the water, or a buildup of debris inside the heat exchanger that restricts water flow.

This fault is more common when heating is first turned on after a long summer break, as internal pump components can seize during periods of inactivity.

Typical repair cost £120-£280 (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 1-A5 fault code

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

Greenstar 8000 Life/Style Repair: £120-£280

Source

Worcester Bosch 1-A5 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