I have browsed the posts regarding failure of the above valve and I think it's a faulty PCB, what are your thoughts please.
Problem: I can get hot water fine but no central heating.
The thermostat is working O.K.
With hot water selected on control unit - If I override (with the knurled button at the end) I can get the WMH lever to manual and lock it in place - result heating.
With heating selected on control unit - If I override (with the knurled button at the end) I can get the boiler to fire up and the pump running but it won't lock in place so it drops back to either W or M (if locked). Locked in position M with just heating selected - nothing!!
Presumably the microswitch is O.K. as it fires up.
Problem: I can get hot water fine but no central heating.
The thermostat is working O.K.
With hot water selected on control unit - If I override (with the knurled button at the end) I can get the WMH lever to manual and lock it in place - result heating.
With heating selected on control unit - If I override (with the knurled button at the end) I can get the boiler to fire up and the pump running but it won't lock in place so it drops back to either W or M (if locked). Locked in position M with just heating selected - nothing!!
Presumably the microswitch is O.K. as it fires up.