2003ish potterton performer 24 noise

[bedford162]

Hi
I have a potterton performa 24, not shure how old it was there when I bought the house.
The problem I have is when shutting the tap off after running hot water it makes a loud sort of vibrating noise for a second.
The boiler works fine with great heating temp and good hot water and flow, its just this noise thats bothering me and it is only when the tap is shut off and only for a second.
Has anyone got any ideas !!!
Thanks

 

[Puddle]

Does it happen when heating also on and ok when heating off or all the time
if when heating on ,possible diverter valve sticking,of could be fan slowing down and vibrating

 

[bedford162]

It does it if the heating is on or off
if the heating is on and the hot tap is opened it switches straight to hw but makes the noise when tap is turned off, and exactly the same with heating off, I can run a bath full of piping hot water with no noise at all untill the tap is turned off then around 1 second of loud noise!!

 

[Puddle]

if it was fan or pump would be longer than a sec or few sec,s if you turn taps off very slowly does it happen,if not then boiler ok probably down to pipe hammer
possible one of the springs has broken in diverter but unusual

 

[stevetheplumber]

sounds like divertor valve problem as that is the part moving when you open or close a tap
i assume this is on all taps if not could be the tap at fault