I had a plumber replace my shower faucet a year ago, a moen single handle positemp I believe, we started getting only hot water, what would cause this to happen? This has happened before that is why I had it replaced, I just can't believe I need to replace this faucet again! I would like to repair if possible. Help please!

There is pressure balanced device installed inside shower cartridge. It is probably stuck in one position. Replace cartridge. See if that helped. Back to you. Milo