Thermostatic radiator valve doesn't work?

[SRJDIY]

Hi, apologies if this is a daft question, but the valve on one of my radiators doesn't seem to be working.

The dial turns fine, but turning it doesn't turn the temperature of the radiator down. I've tested it by touching the radiator, then turning the dial and waiting an hour before touching it again, at which point it feels the same as it did before. The other radiators in my house look like they use the same type of valve; I've tested one of them the same way and it works fine.

Does anyone know what might be happening please? I've attached a picture if that helps.

 

[DP]

Have you swopped the head with another radiator?
Does the defect move with the head?

 

[Madrab]

The dial turns fine, but turning it doesn't turn the temperature of the radiator down.

A TRV doesn't adjust the temp of the rad if that's what you mean? A TRV is just an automated on and off valve - All it does is shut the rad off once the room reaches the temp that the TRV has been set at.

If you mean it won't turn the rad off at all then as suggested, try one that does work, if that still doesn't do it then the valve may be stuck, press the pin with something and see if it moves up and down.