My central heating comes on when the timer shows it should be off. Even when I put the timer to 'off' permanently the heating still is on. I think maybe it does not go off when it should rather than come on when it shouldn't but I'm not sure. At first I thought it was the timer but it may be a sticking valve somewhere. We've only recently moved into the house so its taking a time to notice it is not working properly. Any ideas?

My gas heating is regulated by the thermostat in our dining room. What do you mean by timer ?

When you set the thermostat for say, 70, then when the temp reaches a little below that, then the heat comes on.

Maybe it is some other timer that you are turning off and on, and nothing to do with the heat setting on the thermostat. Is this timer located directly on the thermostat ?

Tick