The shower in the spare bathroom has a single handle moen faucet. When it gets rotated to HOT, cold water still comes out. If you place it in full hot the water stops all together. I have had a plumber come out before and he fixed it in 5 minutes. Thanks.

Shut off the water to the faucet and remove the cartridge clean and lubricate the seals, install the cartridge and check if it works, if not you need to replace the cartridge,see the attach links for info, good luck.

John



Product Detail: L82691 (http://www.moen.com/browsecatalog/catalog/details.cfm?stype=category&ptype=r&product=391&category=1143&finish=44&crow=1&details=product&sku=L82691)

Also the cartridge has inlet ports.see image) that should be checked and cleared. Don't forget to turn the water on, with the cartridge still out, to flush out the supplies and valve body. If none of those work then follow Johns advice and replace the cartridge, good luck, Tom