I did a "simple" cartridge replacement on my shower. The valve appears to be a Moentrol Valve, model 3570 (single handle). It's configured in a shower, with a diverter to a second faucet, a "rain" type one coming down from the ceiling.
I thought I was being clever when I turned the screw on the left and the water shut off - I have since found a drawing that labels it as the Stop-Check valve.
Once my new cartridge was in, the water won't come on. So I opened the stop-check valve screw and voila, the water comes on. Unfortunately, now it won't turn off unless I back the screw in again. I've botched this pretty good.
It may just be that I've messed up the cartridge replacement, but it's so straight forward I can't figure out what I could have done.
Any advice is greatly appreciated! - Mike