[steph93]

When I turn my tub faucet on there is not hot water. The cold water runs fine but when I turn it to hot, there is no water

[massplumber2008]

Steph... what is the name on the face plate of the tub/shower valve? How old is valve and/or home? If no name, check out shower head and if no name there, try to describe it too me. Get back to me

[speedball1]

When I turn my tub faucet on there is not hot water. The cold water runs fine but when I turn it to hot, there is no water

If you answer Massplumbers question he can look up the specs and, hopefully, put up a picture you can work off from. In the meantime let's look at what we have. I can give you a general answer and pinpoint the cause but in the meantime answer Marks questions.
You have no hot water because mineral build up has got into the hotwater pipe and is now clogging the inlet ports of the cartridge. Shut the water off and remove the handle and faceplate. Open up the valve and pull the cartridge. Check and clean the inlet ports of the cartridge and turn the water back on for a moment to flush out the supplies and valve body. That should clear the faucet, however, It will just happen again unless you control the source of the mineral build up. Your water heater's the cause of your problem. You need to flush out your heater on a regular schedule. Let me show you how.
For long life and fewer troubles you should keep your heater clear of mineral build-up by FLUSHING NOT DRAINING on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear. . Don't forget to flush it out every month. Your heater will thank you for it. Hope this helps, Tom