A couple of the radiators in my house have a Danfoss Thermostat on
them (not sure exactly which model of the thermostat but by the looks
of them both I'd say *at least* 10 to 15 years old). Both are turned
up to maximum.

It looks similar to this:

http://www.danfoss-randall.co.uk/Sit...nsor_group.jpg

But mine is of a slightly older design. The principle is the same
though.

Anyhow, the one in the hall works fine - the radiator stays on all the
time and it gets nice and hot and stays that way until the heating
goes off. The one in the lounge comes on okay when the heating fires
up (twice a day) but then goes off when the room reaches what it
thinks is the 'correct' temperature - the thing is I'd like it to stay
on all the time that the heating is on. (Note: there is another
radiator in the lounge that does NOT have a thermostat attached and
that stays on all the time of course).

Is the thermostat likely to have developed a fault? Short of replacing
it, is there anything I can check? I've tried twiddling the setting up
and down, etc but no luck. Don't they have some kind of pin inside
that governs whether the water flows or not based on the temperature?
Perhaps this is sticking at a certain point so causing it to switch
off the water flow incorrectly?

Thanks.