Hot water is lukewarm but Central heating working OK.

[fplumber]

Got a problem with my Potterton 24 combi boiler. The hot water is lukewarm but central heating is working OK. We had this same problem in November 2008 and the insurance (emergency cover) fixed it by changing the Diaphragm (part no. 5111137) in the Diverter valve at the time. It worked OK for about 6 weeks and soon began to get bad again.

I have looked at the microswitch in the front of the diverter valve for the DHW and the piston is moving and engages OK when hot water starts to run.
What I have observed are these

(1). When the Selector is on Tap water only, the central heating is getting hot as well. (Indication of diverter valve fault? - but what fault and what needs to be replaced?)

(2). When the selector is on Tap water only and hot water tap is left running, the piston on the CHW microswitch side also engages. Should this be the case? (If is should not, what is the fix?)

I have already read many entries on the forum which have been helpful towards my diagnosis but now hoping to get a response from someone with the knowledge and experience that can point out resolution to me.

Looking forward to urgent responses.

Many Thanks

 

[Puddle]

Presume the potterton you mention is the performer 24
The chw microswitch you mention is in fact the pump flow switch,this will operate on heating and hot water
The problem you have is a stuck pin in the front of the diverter valve
This is not were the diagram is fitted, this is fitted in the water section fitted to the front of the diverter valve
To repair this problem water section requires removing from front of diverter valve,this is done by loosening two grub screws a rear
heating water requires draining from boiler then front of diverter valve can be removed,unscrewed from rear
Once this done pull out pin from the inside ,if you pull out from outside you will damage o ring seal clean pin you find covered in black crust and silicon greese,replace reassemble, refill boiler and away you go, hot water
You can find exploded view on potterton web site, however they do not let you know the front of the diverter valve comes off and sell the complete diverter valve
I think the only people who sell this part separately is volkera

 

[fplumber]

Just seen this reply. Thank you Puddle