Radiator temp control not working

[Felix124]

Does anyone know how to remove/fix this kind of radiator knob? (I have included a photo) I can turn it but the temperature stays on full no matter what. It feels really loose as if I'm literally just spinning a bit of plastic. If I turn it a bit harder, everything above the metal connector bit moves too (sorry I don't know what it's called).

Fyi, it's a rented flat, two of our radiators are stuck like this and the landlord is rubbish.

Edit: looks like it says 'Temtrol' on it, if that helps.

 

[footprints]

Pretty old I can't identify it offhand but fair bet it is obsolete so spares are unlikely.
As a rule the big nut at the bottom of the plastic unscrews and the thermostatic head comes away, the have a wax or gell insert that expands when hot and pushes down the pin on the valve body they do give up sometimes and leak.
Best bet is to replace it.
Unfortunately in rented accommodation your landlord could get stroppy if you start tampering with the system.
Is there a service contract where the boiler is serviced? If so you might be able to get it fixed that way.

 

[Hot&Cold]

You may be able to remove the trv sensor by unscrewing the large top nut (its a dry connection) it could even be finger tight.

Then re position it there could be locating lugs but the cut out on the white section could be the front and screw it down firmly (just above finger tight) with grips/spanner.

Even after doing the above The valve could be internally broken and the landlord should exchange them.