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.