I have new house and one shower is either all hot or all cold. The shower head in the off position is down and when I turn it to the left its all hot. center is off and right is is all cold. I tried adjusting the plastic adjustment ring and that worked a little but is there a way to make is so it goes off to all cold mix then all hot like my other shower is? Also if this fix can be made by changing the cartage can someone help me identify the brand based on the picture attached.
It looks like you have an issue with the mixing valve which looks like this -
More specifically it is probably due to an issue in the cartridge which is the front part of the mixing valve and is usually a white plastic cylinder that look like this -
These are in the wall right behind the shower handle. It is likely that something is either jammed up (sediment) or broken in the cartridge. If you open things up and take pictures we can help more.