Originally Posted by
Milo Dolezal
It would really help if you post the brand of the faucet, photo, or / and your location. Otherwise, there way too much guessing .....
Anyways:
You have pressure balanced, temperature controlled valve. There is a pressure / temperature balancing device inside the faucet. It may be a piston, ball, or spring loaded small rod. That device moves from hot to cold, and vice versa, balancing the mixture of h/c water. What is happening is that that device is probably not sliding freely, is calcified or has some kind of debris in it, and as a result, it becomes stuck in one position. You have to open the faucet, remove the cartridge and most likely replace it with new one.
Also, and it addition to the above, you may have stripped handle that doesn't allow you to turn stem around to close water.