No Hot Water

I have a single handle Moen shower. When the handle is turned to cold the water flows fine. When the handle is rotated counter clockwise to hot, the water stops flowing. What could be the problem and hpw can it be fixed? The only access is through the hole where the faucet/handle is at.

Assuming you have the PosiTemp type ( you don't pull to turn on) it sounds like the balance spool is stuck. Get a new Moen 1222 cartridge.

How does it turn on?
Do you turn it?
Or,
Pull it out?