Combi 80 fan query

[Bmt]

I have a Potterton combi 80 that I have recently noticed the fan running continuously after the demand for hot water is finished(tap turned off) and no CH on, the fan runs for about 5 minutes and then switches off, this never used to happen. I had a new diverter valve and pump fitted in january but have only become aware of the fan problem lately.
Any ideas or suggestions greatly appreciated.
Thanks

 

[ChrisR]

Check the hot water flow switch (puts red light on, on pcb) is going off properly. They stick.
Try it on CH - same or not?

Otherwise - Ultimately the fan is controlled by the pcb, which is practically a consumable part on your boiler. I expect you've had at least one new one already.