Sometimes the compass will loose it'* calibration. When this happens CALIBRATE will appear on the display.
Make sure you do not have our rear defog on during this.
Drive your car in to a large open area such as a empty parking lot.
Press and hold the MODE button until the calibrate light appears.
Release the MODE button. The heading display will start to rotate.
Drive the car in small circles. No faster the 10mph (16km/h)
Drive in circles until the CALIBRATE light goes out. This usually takes 1 to 5 circles.
The compass should now be calibrated, you will know this when the direction bars are on and the calibrate light is off.