Radiator not working?

Another possibility is that the thermostatic valve has stuck closed. If you remove the controller to the valve (the plastic rotary knob with the settings on it) Then you can see a small 4-5mm metal pin that can move in and out about 3-4mm under the control of the knob. If a radiator has been switched off for along time then this pin can get stuck in the closed position. A pair of pliers gently exercising the pin can loosen it and save a more expensive repair and indeed draining down your system in order to change the valve. Snag is removing the rotary knob as each manufacturer's design is slightly different. I've just finished the above job but unfortunately only figured out how to take the knob off after I had removed it from the radiator. I fitted a new one and at least now I have a spare and know how to check this in the future.

Mark
January 2011

Assuming the radiator valves are open - control valve on one side and lock valve on the other, usually with a little plastic hat on it....

Bleed the radiator.

You will need a special little tool like a key (Radiator Bleed Key) with a square hole at the business end. On the top of one side of the radiator should be a bleed screw- a little square stud is all you will see. Unscrew it (anticlockwise) a turn and a half with your little key (any hardware shop or a neighbour) and hold a rag close to the hole - you will hear air hissing out. When water comes out - it will probably be dirty black water - turn the key clockwise and close off the bleed valve.

Your radiator should now warm up.

When you have the time, check the other radiators - any with a cold area at the top will need bleeding. You can also bleed them when cold but water may come out immediately so hold the rag close to avoid a mess on the carpet.

DO NOT TAKE THE BLEED SCREW OUT COMPLETELY - just a turn will be enough for the air to come out.

Richard Buxton
October 2008

you might have an air lock in it.. there is a valve that needs to be opened to allow the air to be removed.

coldini
October 2008