The thermostatic radiator valve in a spare bedroom is stuck closed. It is about 5 years old and has been off since it was fitted, apart from once a year when I turn the dial up to refresh the water. Now when I turn the dial to max, the radiator remains cold.
It is a Danfoss valve; should I be able to pull the housing off to inspect the workings?
For radiator valves, the advice is similar once the valve cover is removed. See our removing a radiator project for this job and then use a spanner to undo the peg which extends from the valve body. With thermostatic radiator valves the situation is often a great deal simpler. When you have removed the head you should, in most cases. See a pin sticking out from the body of the valve. A gentle tap with a hammer should release this nicely. "
Remove the adjuster knob then tap the housing with a hammer - sounds drastic, but it's the only way I've been able to get ours to work. Then, keep gently tapping the small brass pin that protrudes until it it moves freely.
but pay careful attention to the word 'lightly' when tapping. This is best done very rapidly on the side of the valve casing. It will free the neoprene valve washer, which has become stuck to the valve seating.
Thermostatic valves should be operated once or twice a month throughout the year to prevent this happening, and when you close the valve don't use excessive force - it jams the washer too tightly onto the seating.