I've had it with these things. They don't "work". They turn on, and make numbers, but that's about it. The temperature reads real close when you first start the truck (if it's been sitting overnight). But then it never changes. The Compass isn't close enough to rely on if you were lost and needed to know what direction you were traveling. Typically it's at least one Cardinal point off. And yes, I've done the calibrate.
I've had three of them. They have all acted the same: Useless. There's a lot of work to run the wires to it and the sensor. Took me most of a day to install mine. Based on three-of-three failures, I won't do it again.