hot water is missing

My Moen shower/ tub single lever faucet only lets cold water out of faucet. When faucet lever is turned fully counter clockwise, the flow of cold water is reduced to a drip and remains cold. What is the solution to repair or replace the unit? Thanks. Bumper

You could try replacing the cartridge.

Depending on WHICH Moen valve you have it either has the balancing spool in the cartridge or screwed into the body of the valve. Whichever you have, take it out and tap it on the floor, then shake it. IF it "rattles" you fixed it so you can put it back into the valve, otherwise get a new one.