No cold water in shower

Hi, I cannot get cold water through the shower mixer, I have tried to calibrate it but can only get it to luke warm, help needed please. I have attached a picture of the set up of this shower unit.
Thanks
John

I cannot get cold water through the shower mixer

Click to expand...

No cold?
You may have a thermostatic valve there, and it may just be giving you a tight range.
Sometimes you can remove the valve and reinstall the knob in a slightly different postion.

That type of valve often has two internal check-valves, and one may have jammed closed. They often also have an inlet filter, and that may be clogged up. Or, the thermostatic cartridge could be shot. See if you can dig out the installation instructions which will have a parts diagram. If you can't find it, you may be able to get one from the manufacturer's website, or you may have to call their tech support. Some of those valves have a lifetime warranty, so if it needs parts, they may send them to you for free...doesn't hurt to call and check.

Thanks Jim, unfortunately there were no instructions and I had a British Gas plumber out and he couldn't identify who the manufactures were, to be honest I'm not sure he knew what he was doing, any ideas how I can find out who the manufacture is?
Thanks
John

Thank you Terry I am a complete novice and wouldn't know a valve from a half hitch,
John

SOmetimes, you can figure out who made it by looking at the cartridge which requires taking the trim off first and maybe removing it.