9.C Low

Worcester Bosch 9.C Fault Code

Also written as 9C — same fault.

The Worcester Bosch 9.C fault code means: your boiler is displaying its current power level because a technician is likely testing the system or a specific testing mode has been left on.. It appears on 1 Worcester Bosch model 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: Actual heat output (%)

What causes the Worcester Bosch 9.C fault?

This code appears when the boiler is placed into a manual testing mode, usually by a technician checking the system's performance. It indicates that the control board is temporarily overriding normal operation to run the burner at a fixed capacity. If you see this and no engineer is present, the testing dial on the front of the unit may have been moved or left in the wrong position.

Typical repair cost £0-80 (including labour)

DIY fix possible

Press the Reset button once to clear the displayEnsure the chimney sweep or service mode switch has not been accidentally activatedTurn the power off and back on at the fused spur if the code persists

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Worcester Bosch models that show the 9.C fault code

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

Source

Worcester Bosch 9.C 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