I've never had to calibrate a gauge before but this week was the week. I went through 3 different temp senders on hand, one for sure is supposed to work with the gauge. All read very high, one pegging out. I knew there was a way to adjust them but had never done it. So here's the intel if you need to do it yourself. I took a crap gauge apart to learn the internals before I accidentally broke a nice brand new gauge. Back side of the gauge has 2 spots with little slots. They don't screw with a flat head but rather slide on a pivot. Both adjust the readings. Doesn't take much to adjust it.
So what was the step-by-step procedure?