Either the radiator is blocked, unbalanced, full of air or not piped up correctly. In simple terms your radiator is does not have enough hot central heating water flowing through it to make it get warm. We are assuming everything else is working and all the other radiators are getting hot – so the problem is isolated to an individual radiators.
The first thing to do is bleed the radiator. If the radiator is full of air it will be cold at the top and warm at the bottom. But by bleeding the radiator you can easily rule out this simple fix. Use a bleed key to carefully let air out of the top of the radiator until you get a little bit of water.
The second thing to do is to make sure both valves are open. Open up the valves using a spanner. Sometimes Thermostatic valves can get stuck so you might need to check that the pin is moving freely when you open them up.
If neither of those things work then it’s probably time to call a plumber. Your system may need balancing, the radiators may need a powerflush or there may be some other issue with the valves or the pipework
