Worcester combi motorised valve problem

[crispibits]

Hi all,
Can't quite find my problem here, and I have searched, honest...

First off, it's a Worcester 15/19 Oil fired combi.
Problem:
Hot water ON, CH ON.
Hot water *very* hot. Rads cold.
Switching the valve thing so that it holds on CH resolves the problem. This suggests that the valve (or electric supply) is knackered. This is after replacing it two days ago - it worked when I first put it in. Attempting to turn the valve manually with the motorhead off seems quite easy. Any ideas what would cause the motorheads to die so quickly, or any ideas what else it might be?

 

[Agile]

I dont seem to be able to understand what you are trying to explain.

I assume that you realise that your boiler provides either hot water OR central heating but not BOTH !!

Tony