We had someone out to look at our water heater a couple of weeks ago because we were only getting cold water to the shower. They said the scald guard was turned to all cold. We are now having the same problem again. Where is this located and how do we check it?

The scald guard is part of the plastic gear mechanism the handle attaches to. The guard prevents the valve from being opened to totally hot only with no cold. The actual mechanism varies from manufacturer to manufacturer but that basically how they work. They usually can not shift by themselves, Moen for example is a tooth gear that must be removed, rotated and reinstalled. Whatbrand valve do you have, model too if you have it?