heating not working on my primaf 60 potterton boiler?

is it y-plan or s-plan 1or2 valves.y-plan has 3 pipes going to a valve,s-plan has 2 pipes going to a valve.if its y-plan you need to check if it has 3 wires to the cylinder stat and if there is a wire in the clock for hot water off so if the cylinder stat is satisfied it powers the clock for heating,if not has the clock got a setting for gravity this will automatically power the valve when water satisfies

jim
February 2009