Heating Not Switching off

[mig]

A problem has arose on my central heating in that the heating stays on continously despite the setting on the thermostat. This generally happens first thing in the AM. I find that if I switch the heating off and then back on again (either at the controller or the fuse board) it seems to behave itself in that if I turn the thermostat down I hear it click and the boiler shuts down and it generally behaves for the rest of the day.

Any thoughts ??

System is a normal gravity-fed system.

[jwxfs]

stuck motorised valve when the water is also on?

[tomkent45]

Probably something wrong with the valve. I suggest you buy a new valve, will cost around 40 to 50 quids and you can change it your yourself.