Tampered thermostat radiator valve control head

[Shocker]

Hi,

One of my house mates has intentionally broke a couple of thermostat radiator valve control heads, so that they are permanently on. I am rather furious that he has done this because the rooms are hardly used and they leak a large amount of heat. He has also done this on the sly hoping that i wouldnt find out.

Fortunately, he has gone on holiday for a few weeks otherwise i would have an argument with him and there would be tension in the house for quite some time. I want to repair these valves before he gets back without replacing them and without calling a plumber.

The control heads are Caleffi 200. The heads can completely rotate between fully off and on but like i said, the radiator is always on regardless of the setting that the valve is on.

This is a picture of the control head
http://www.caleffi.com/Resources/cale_immagini/200_th.jpg

And this is the good piece of documentation i have i have been able to find.
http://www.caleffi.it/en_IT/Technical_brochures/01034/01034.pdf
There is a good diagram of the control head on page 3.

Ive had a look at the control head to see if i can fix it but i just cant seem to work it out.

Does anyone know how he might have broken the head? And does anyone know how i can the remove plastic shell/housing without damaging it so i can fix it?

Any help is much appreciated.
Rob

 

[SpecialK]

See the silver ring at the bottom of the plastic head? Unscrew it.
Is there a pin underneath that moves up and down?

 

[Shocker]

See the silver ring at the bottom of the plastic head? Unscrew it.
Is there a pin underneath that moves up and down?

Beautiful! that was exactly what he has done, he has taken the control head off and removed the pin that presses down on the valve.

Thanks so much!