HELP.
I have a potterton Suprima 70. We had the pcb replaced when we moved in about 3 yrs ago.
Basically, when the hot water is due to come on, it keeps clicking on then off, but won't stay on.
If the heating comes on at the same time then it seems to work ok.
The hot water, if left will eventually light and come on by itself. This can take 20 mins or longer.
Lee
July 2012