Be recruited to sort out a problem on a friends heating.
My knowledge stops after gravity HW systems!
Their system has conventional boiler and programmer, cylinder thermostat and three way value (Pipe in - and the Port A heating, Port B HW - Drayton Flowmaster 2)
HW is OK
When Central heating is selected only HW heats - rads are completely cold - pipe work in airing cupboard is red hot.
if I push the little lever on the 3way over from HW to CH (very hard to push) and hold it then the rads get warm - when I let go again the valve moves back to HW and the rads cool.
I am guessing that it is the motor on the valve? Is this right? Could it be (or likely be) anything else? What would I need to test to find out?
If it is the motor? is this a standard part or does it depend on the valve? (in this case Flowmaster 2)
Can anyone help?