Please can anyone help a DIY guy? ...CH problem....

[vintageaxeman]

Well people, I've solved it.
I decided that if all the connections were present and correct, and that all the valves, components and so on were ok, then it must be the wiring itself. What I found was that one wire from the programmer to the wiring centre was fractured and had intermittent contact. It's the one that turned the pump and valve on when heating was called for.
SOLVED!!!!
Thank you all so much for your help!

 

[telectrix]

thanks for getting back . glad you fixed it.

 

[Barry White]

Always nice to get an end to a thread. Thanks for reporting back. Do come again.

 

[Pat H]

If it was the diverter valve then the boiler and pump would still fire up. As they don't it has to be programmer or thermostat.

 

[tony mc]

Not if there is a break in the HW off cable!

If the controller is calling for heating and not HW and only the white wire has 230v and the grey wire is not getting 230v the valve will not drive across putting 230v on the orange to fire the boiler and pump up.