Ian Cornish presented the following explanation :
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

The 'motorised bit' is called the actuator. It is probably the actuator
sticking and is in need of replacement. Is it a spring return type?

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org