I have an issue which I believe is a mid position valve fault.
Ch is on as normal and controlled by thermostat, simple mechanical one. Suddenly radiators are hot despite ambient temp already being warm. Thermostat clicks on turning back and forth but does not turn off ch.
At the same time the boiler won't fire up for the hot water despite the tank thermostat suggesting it should.
Turning just hw without ch does not change this and it won't fire the boiler.
I'm thinking acentuator on valve has gone kaput.