Apologies for probably not using the right technical terms...I'm not a plumber.
However, I appear to be having issues with the motorised valve thingy on my heating system. Before calling out a plumber, I'd like to know more about it, and likely causes of problems. The problem is that it switches from heating to hot water OK, but no matter what I try, it will not switch from HW to heating automatically - I have to use the little lever on it to move it back.
Is this a wiring issue, or just a knackered valve ?
TIA,
Ian