Towel radiator valves stopped turning

[ahac69]

Hi,
I've just replaced a valve on a radiator and had to drain the system first. System is sealed combi boiler Worcester.
After refilling I found that a towel radiator in the bathroom where the boiler is will not work. Previously I could turn both the silver valves on it quite a few times each to adjust the heat. Now however they move about a quater turn and no further.
The pipe to one gets hot and I've bled them and there's no air in them.
They worked fine before but not now.
Any ideas?

 

[HERTS P&D]

The worm inside the valve has come undone, it will now need to be drained down and remove the valves and refix or replace.

Andy

 

[ahac69]

Thanks for getting back to me. I had already managed to get them working by doing what I think you suggested purely by chance. I removed the end plate and then loosened the first nut. I then replaced the outer case which had teeth on it to turn the spindle. The spindles began to turn again so I took the case off again, tightened the nut and replaced the outer case.
The one thing I hadn't done which you sugested was drain the radiator first so there was a fair bit of water spilt when I was turning the spindles. This also made it harder to fit them back in as I'd turned one so much it came out.
Anyway managed to get it all back in and rad now working.
Thanks for the advice.