Low Warning
9.F on Worcester Bosch Greenstar CDi Compact

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.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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 over-run time (CH mode)

What causes this 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

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