Worcester 241 junior?

If your cold radiator has a Thermostatic Control valve then the valve may be stuck in the closed off position - a common fault.

Remove the control head (an easy job requiring no tools) and notice a small brass pin about the size of a match - pull it upwards with a pair of pliers - wait for the radiator to get warm then refit the control head.

Good Luck...
November 2016

One radiator has gone off but all the others are OK; getting hot, etc?

Doesn't the fact that the other radiators are getting hot suggest to you that the boiler is actually working?

Have you checked the radiator valves? Are they properly open (Note: one may not be fully open if it has been adjusted to "balance" the system.)

If there is a thermostatic valve, check the valve head is properly attached to the valve body.

Check the radiator needs bleeding (Note: You may need to repressurise the system if there was a lot of air in the rad. Check you know, understand and are equipped to do this)

You may need a central heating engineer if not confident/competent
November 2016