Basically the pump only runs when the cylinder calls for it.
The valve appear to do all the right things, i.e.:
CH H
HW W
CH&HW M
So 2 issues:
1. It's just that when only the CH is on, the pump doesn't run / boiler doesn't fire
2. IF both are on, initially everything fine (valve in M position, rads hot), however once the cylinder is up to temp, the pump switches off - so you end up with a cold house, even when the CH is set to continuous on the programmer and the Room stat is asking.
As I understand it, there are two switch wires - white & grey, and if either is live they should make the orange live to run the pump?
What you need to do is set programmer to c/heating only
then
a; check if there's power to the white wire on valve assuming stat is calling
b; with valve in mid position the orange wire should be live if not its the micro switch
c; if there's no power to white wire which is usually on connector No 5 check connector No4 which is feed from programmer to stat
In other words all things being equal you should have power to connector No 4-5 and 8
toptrish
November 2013
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.