heating only turns on if hot water is turned on then off...

[cobyh]

hi, have a worcester highflow 4.5. working fine until recently where the central heating stopped coming on, although I can manually operate the diverter valve and have it heat that way (if I lock the diverter valve open). So I thought the synchron valve was the issue, replaced that. Now it seems that the only way I can get the central heating to come on is if I turn the hot water on the off again... or lock it in place like before. (making the timer redundant). any help would be greatly appreciated.

thanks
coby

 

[Vee]

Have you checked there is a live feed to the diverter valve from the external controls?