I have a Grohe shower valve that I need to determine the model. It has one control for the temperature and then one valve that turns the water on and off. I know that the valve was installed prior to 2004. I can post pictures of it later, but any suggestions are appreciated.
Call Grohe! Their tech support is usually pretty good, and I've had them e-mail me the install manual when I've misplaced it for future reference. It sounds like a thermostatically controlled valve...if the cartridge is bad, they're fairly expensive. WHen replacing it, you must also recalibrate the temperature control knob, and that takes an accurate, fast reading thermometer, a little time, and the instructions.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013