T3 Low

Worcester Bosch T3 Fault Code

The Worcester Bosch T3 fault code means: your boiler is performing a routine check of its internal pump and may temporarily pause normal operation while it completes the test.. It appears on 11 Worcester Bosch models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Pump test – checking the basic pump

What causes the Worcester Bosch T3 fault?

This occurs when the boiler performs a scheduled diagnostic check to ensure the internal pump is spinning freely and moving water correctly. It is a standard safety routine rather than a breakdown, though it can sometimes trigger if the pump is struggling to start due to internal wear or a buildup of debris. Under normal conditions, the code will disappear automatically once the test is successfully completed.

This is more frequent after long periods of inactivity, such as the first time the heating is turned on in autumn, as pumps can occasionally stiffen when not in use.

Typical repair cost £0-80 (including labour)

DIY fix possible

Wait for several minutes as the code usually disappears automatically once the test is finishedMonitor the boiler to ensure it returns to its normal temperature displayIf the code persists for over an hour, try a simple reset using the 'Reset' button

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Worcester Bosch models that show the T3 fault code

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

Source

Worcester Bosch T3 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