My shower faucet seemed to be on the frizz. I can only get either all cold water or all hot water. Nothing in between. I suspected maybe the cartridge was dirty from the hard water so I removed it and soak it in cider vinegar for 2 days. Still same problem. So I finally bought and replaced the cartridge (Rohl 7912), but am still getting the problem. All cold or all hot! Please help.