My home is past the 1 year builder's warranty and I realized that there is no hot water in the shower in my guest bathroom (there's hot water in the sink). I think it's a problem with the installation of the knob that turns on the water. When faced down, it's off; when turned to the "C" on the right, I get cold water; when turned 90 degrees, it's warm water; the problem is as I start to turn to "H" on the left for hot water, it begins to turn off. Anyone has any ideas? There should be hot water if the whole house have hot water and the sink in this bathroom have hot water.

Can you furnish us with a brand name and model? Back to you, Tom

Speedball1, thanks for answering. It's made by Moen, I don't know the model but it looks like the one on the link below.
MOEN Adler Single Handle Shower with Knob in Chrome

Model # L82691 Internet # 202060909
Store SKU # 242983

The only difference is the know is handle, it's like the clear plastic kind. Hope this helps.

MOEN Adler Single Handle Shower with Knob in Chrome - L82691 at The Home Depot

Chances are a bit of trash is blocking the inlet ports on the cartridge.
Shut the water to the valve and open the valve (see image) to remove the cartridge, (see image). Check and clean the inlet ports at the base of the cartridge,
Now, with the valve still open, turn the water on for a few seconds to flush out the supplies. N reassemble and test. Better now? Regards, Tom

Thanks, I'll take it apart tonight and try it.