Make radiator valve again common
If a radiator does not get really hot (even though it is vented) or if it does not turn off properly, you can do the following.
First, remove the thermostatic head (loosen the rear large screw ring and carefully pull the head off). Make absolutely sure that the rear small cramps on the head does not break off.
You can now see a small spigot on the radiator valve. This pin can be stuck by oxidation or by slightly adjusting the valve.
This pin must be easy to move. If it hangs tight, then oil the pin a bit and then pull it in and out with a pair of pliers CAREFULLY. Then he should move easily again.
Then the thermostatic head is replaced in reverse order.
This should be done preventively in all radiators annually to ensure the proper functioning of the radiator. In addition, you can also save heating costs under certain circumstances.
But if you do not feel confident enough, you should contact an installer.
