No hot Water on Single Handle in Shower

I've got a Kohler Single Handle valve in my guest bathroom, and the hot water will ONLY come on it the fully open position at 12 oclock. And then it is just a trickle at that. I have plenty of cold water but no hot. I've got hot water everywhere else in the house, and even in the same bathroom. What can I do to possibly remedy this problem. I don't know what the model is at all, I looked on the handle and the numbers on the handle aren't a model number on the kholer site apparantly. Any help would be appreciated.

i am not a pro. but i had that same problem a few years ago. it was the cartridge behind the handle. swaped it out, all is good. HD etc, should have em.

It actually wasn't the cartridge, my kids had been moving the handle up and down really quick and I didn't think anything about it. Then when I pulled everything apart I noticed a chunk of rubber on the back of the handle control. When I popped the cover off of where the mixer disc is, on of the mixer "funnels" was caught in the mixer itself. So when we were turning it to hot, it was just getting pinched, not letting any water through. Saved me a little bit of money and fixed the problem. Little brats. LOL