If you want to check what the reading of the in-car temp sensor is, hold down the rest button while the A/C is on for at least 5 secs. Then two numbers will start to flash, the first one will be the number of what value is being displayed, the second will be the value. If you do a search, you will find a list of what the values correspond to. If I remember correctly, the first value, number 1, will be the in-car temp sensor's reading in degrees F.
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record