BoilerFaultCodesWorcester Bosch 9.F Fault Code
Also written as 9F — same fault.
The Worcester Bosch 9.F fault code means: your boiler's internal pump is running longer than it should after the heating has switched off, which often indicates a communication error or a trapped signal.. It appears on 1 Worcester Bosch model in our database.
Technical description: Pump over-run time (CH mode)
What causes the Worcester Bosch 9.F fault?
This fault occurs when the boiler's internal computer keeps the water pump running indefinitely because it hasn't received the signal to tell it the heating cycle has finished. The most common reason is a communication error between the main circuit board and the pump, or an electrical component on the board getting stuck in the 'on' position. While the boiler may still function, this constant running puts unnecessary wear on the pump and wastes electricity.
DIY fix possible
Locate the reset button on the front control panelPress and hold the reset button for five secondsWait for the boiler to restart and check if the code clears
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the 9.F fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 9.F 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