Only Hw when heating is on, pin doesn't return

[Julie Brown]

Having a problem with potterton 30 he. Only hw when ch is on. I've refurbished the diverter twice! Because this problem persisted. Changed pump, pressure switch and pcb board. Changed thermostatic switches as was very hot. But the pin does not return to fully off position, half way down then 60 degree warning light appears. Which is pressure or pump problem it says. It's been cleaned the water in system. But now the hall radiator is cold but rest of house is warm. Still only hw if heating is on. If anyone could help I'd be grateful thank you. After it times out on timer the warning light comes on as the pin stays half way up.! Any ideas would be great. Thank you...

 

[ianmcd]

on the pump proving diaphragm, remove the diagphragm and there is a tiny orifice under it, give that a good clean out with a piece of wire or something

 

[gas112]

So when you turn hw tap on does the hw demand light come on