To calibrate your RP2: Find a location where it will be safe to make a U-turn (an empty parking lot is ideal). Park the vehicle away from other vehicles, leaving the engine running. Switch on all electrical accessories that are normally used (heating fan, radio, etc.).
Press and hold the reset button for 3 seconds (cardinal points, numeric digits and the word "CAL" will flash) wait 5 seconds to avoid initial, unstable condition then immediately begin driving the vehicle slowly in a circle. Complete at least one full 360 degree circle while the flashing "CAL" is displayed. After approximately 10 seconds the flashing "CAL" will disappear and the cardinal points and the numeric digits will stop flashing. The calibration of the compass is now completed. Check that the compass is providing readings that appear to be correct.
For best results mount the outside sensor probe either under the front bumper or in the front door frame 2 inches under the hinge. Mount the inside unit away from electronics, such as speakers, and out of the sun.
The switch to change from Celsius to Fahrenheit is in the battery compartment under the battery."