High
T3 on Worcester Bosch Junior 28i

Your boiler is checking if the internal pump is moving water correctly and has detected it might be stuck or failing.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Pump test – checking the basic pump

From this model's manual
Verified against the Worcester Bosch Junior 28i installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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