Traditional Thermostatic Shower Valve - possibly sticking

[gwernybwch]

So I have am getting lukewarm water in my shower, yet the water in the pipes right up to the mixer is hot as hell.
I'm guessing that there is a valve of something sticking inside.

Any tips on how I can unseize the valve? Or does anybody know if or how this can been taken to pieces?
All I can see is a big allen screw at the bottom which is the water by-pass and there are three small allen grub screws which hold it to the backing plate, apart from that there isn't anything obvious as to how it comes apart.

Any help appreciated.

 

[muggles]

The HR logo will either unscrew or prise off, and the ceramic handle should also unscrew. This will then reveal screws holding the whole lot together

 

[gwernybwch]

Thanks for the reply.
I've taken the logo off and I can see a screw with a Philips head holding on the chrome knob. I've tried to get the screw out with a normal screwdriver and then an impact screwdriver, but it isn't budging. Any tricks for removing the screw? It looks quite a soft metal, so I don't think that it would take much abuse.

Thanks in advance for any replies.

 

[Hot&Cold]

Youl need a new screwdriver bit to give a very good snug fit in the brass screw,try to very slightly tighten the screw this often frees it enough and unscrew as usual. have you tried a squirt of dismantling liquid ? tried pouring a kettle of freshly boiler water over the brass screw then undo ?

If your shower is actually the one above. Google search videos= showerdoctor ultra finishing 1/2 inch shower valve

Should be many videos including calibration for that traditional style valve.

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