1995 Pontiac Bonneville Owner's Manual - Page 120

3. Release the MODE button. The heading display will start to rotate. 4. Drive the car in small circles. Don't drive faster than 10 mph. 5. Drive in circles until the CALIBRATE light goes out. It usually takes 1 to 5 circles. The rear defog system can affect accuracy, and the compass corrects for the rear defog. However, if the rear defog is turned on while making sharp turns, the accuracy may be off. When you turn the rear defog off again, the accuracy returns to normal. 6 . Your compass should be calibrated. You will know this when the direction bars are on and the CALIBRATE light is off. Do not turn on the rear defog if you are trying to calibrate. The system will not allow the calibration. You will hear the chime,and CALIBRATE will flash for a few seconds. Compass Accuracy: Your compass may show different headings around bridges, power lines, large metal objects, and steep hills. This is normal and is true of compasses in general. If you put large metal objects like golf clubs in the trunk they could affect accuracy. If the accuracy is close, the compass will adapt to these objects over time. If you use an antenna with a magnetic base, it is best to mount it away from the center the trunk near the rear of window. Be aware that metal objects are sometimes buried in the ground. They can affect accuracy and you maynot know they are there. As an example, many concrete roads have metal reinforcements inside.