Broken thermostatic radiator valve, or something else?

If they're left off (as in closed) for a long time, like over summer, they can stick in the off position. You might get lucky hitting them with a hammer etc otherwise you might need to remove and clean it which would require some sort of draining. This is assuming that the outlet valve isn't closed of course.

Remove the body of the TRV by turning the ring at the base. You should see a little pin that the TRV pushes up and down to open and close the valve.

This should move up and down with reasonable pressure. If it doesn't, it may be stuck closed and need freeing.

Do this by tapping very gently with somethingto free it.

Pulling the pin up and down a few times with a pair of pliers usually does it (they only move a few mm), but be careful not to burr it where it enters the valve body.

Google this group on "stuck trv" for more advice, e.g.

The valve at the other end often silts up too. Try opening it up for a while, but mark its position and count the turns to return it to where it was, as they are precisely set to "balance" the system.

Chris

Remove the control top - it should have a collar that simply unscrews by hand. Underneath you'll see a 'pin' sticking up. That is the actual valve. It should push down under thumb pressure and spring back up again unaided. Check with a working one to see what I mean. Your faulty one is almost certainly just stuck. Tap it gently down with a hammer handle etc and it will hopefully free.

If it's very old there may be signs of a water leak from around the pin. If so best to have it changed rather than attempt to free it as it will leak even more when freed.

Some cheaper TRVs have a life of only about 5 years.

Thanks Dave and everyone else for your advice -- I'll have a play with it and see what I can see. I just had a quick look at one of the TRVs at work and I see what you mean about the pin.

Cheers

- Ian

Note that the pin only moves a little - about 3-4mm.

If it doesn't prove to be that, then you may have an air bubble in the pipe.

This can usually be cleared by closing all other TRVs, opening the offending one and perhaps winding up the pump speed.

Thanks to all that replied -- I sorted this out on Saturday. Tapping the valve and pin gently didn't have any effect, so in the end I very gingerly got hold of the pin with a pair of pliers and pulled ever-so-gently, and it just popped back up. After that, it's moving (relatively) freely.

Thanks again, you saved me a plumber's callout!

- Ian