Stuck mixer tap

[JoeS]

Hi all, i have recently moved into my first property so i will probably be asking a stupid question. In my bathroom the bath is fitted with a hot and cold tap and in the middle a shower thermostatic mixing valve. the Thermostatic valve is only giving out cold to very cold lukewarm water. When you turn shower on the temp identifier spins with the shower control i have attached a couple of photos. Any ideas how i can solve this? Any help is greatly appreciated.

Cheers in advance

Joe

 

[nickatliberty]

When you open the tap up, does it have a cartridge inside?
And is the cartridge intact or is it cracked?
I have seen a similar problem with a cartridge where the plastic that connects to the selector is sheared. On the hot water issue I would hazard that the valve for it is stuck.