Questions and Answers

Jeep Grand Cherokee Compass Q. Hello Vince, I talked to you on the phone a few week ago with an O2 Sensor problem on my 1997 Jeep Grand Cherokee. I had my local Chrysler dealer check it out and you were correct (it was giving the Jeep to rich of a mixture). Now I am stumped on a compass problem. It hasn't worked since I have owned the Jeep, and I have finally gotten around to trying to get it fixed, but am unable to.

The jeep place said I would have to bring it in with a minimum $60 charge but I don't want to do that if it is something simple. When I tried to fix it, I held the two buttons on the top display for 10 seconds and set my variance. Then I turned the vehicle in three 360° turns, thinking that would do it. The CAL sign still appears and the compass does not function.

The guy at Jeep said I may need to demagnetize the roof first. I did not know if you know of a way for me to do that, or if I am missing a step in calibrating it.

Thanks for the help,
Brock

A. I have always thought that a compass is near about the most useless thing they ever put in a car. They are finicky, rarely work right and a PITA to service. Besides, if you need a compass to know where you are, you shouldn't be behind the wheel of a car.

I would try calibrating the compass again. Go buy a compass, any kind will do. A ten cent compass is just as good as a $25.00 compass. Find an empty parking lot that will allow you to be at least 100 feet from the nearest building. Using the good compass, set your car pointing dead north and calibrate the compass. If it still doesn't calibrate, you can get a degaussing tool at a Radio Shack store. Make sure it meets the specifications outlined below.

Calibrate the compass manually as follows:

1. Start the engine. If the compass/temperature data is not currently being displayed, momentarily depress and release the Step button to step through the display options until you have reached the compass/temperature display
2. Depress both the U.S./Metric, and the Step buttons. Hold the buttons down until "CAL" appears in the display. This takes about ten seconds, and appears about five seconds after "VAR" is displayed.
3. Release both of the buttons.
4. Drive the vehicle on a level surface, away from large metal objects, through three or more complete circles in not less than 48 seconds . The "CAL" message will disappear from the display to indicate that the compass is now calibrated. NOTE:
   • If the "CAL" message remains in the display, either there is excessive magnetism near the compass, or the unit is faulty. Repeat the demagnetizing and calibration procedures at least one more time.
   • If the wrong direction is still indicated in the compass display, the area selected for calibration may be too close to a strong magnetic field. Repeat the calibration procedure in another location.

To demagnetize the roof panel and the overhead console forward mounting screw, proceed as follows:

A degaussing tool (Special Tool 6029) is used to demagnetize, or degauss, the overhead console forward mounting screw and the roof panel. Equivalent units must be rated as continuous duty for 110/115 Volts and 60 Hz . They must also have a field strength of over 350 gauss at 7 millimeters (0.25 inch) beyond the tip of the probe.

1. Be certain the ignition switch is in the Off position, before you begin the demagnetizing procedure.
2. Plug in the degaussing tool, while keeping the tool at least 61 centimeters (2 feet) away from the compass unit.
3. Slowly approach the head of the overhead console forward mounting screw with the degaussing toot plugged in.
4. Contact the head of the screw with the plastic coated tip of the degaussing tool for about two seconds.
5. With the degaussing tool still energized, slowly back it away from the screw. When the tip of the tool is at least 61 centimeters (2 feet) from the screw head, unplug the tool.
6. Place a piece of paper approximately 22 by 28 centimeters (8.5 by 11 inches) , oriented on the vehicle lengthwise from front to rear, on the center line of the roof at the windshield header. The purpose of the paper is to protect the roof panel from scratches, and to define the area to be demagnetized.
7. Plug in the degaussing tool, while keeping the tool at least 61 centimeters (2 feet) away from the compass unit.
8. Slowly approach the center line of the roof panel at the windshield header, with the degaussing tool plugged in.
9. Contact the roof panel with the plastic coated tip of the degaussing tool. Be sure the template is in place to avoid scratching the roof panel. Using a slow, back-and-forth sweeping motion, and allowing 13 millimeters (0.50 inch) between passes, move the tool at least 11 centimeters (4 inches) to each side of the roof center line, and 28 centimeters (11 inches) back from the windshield header.
10. With the degaussing tool still energized, slowly back it away from the roof panel. When the tip of the tool is at least 61 centimeters (2 feet) from the roof panel, unplug the tool.
11. Calibrate the compass and adjust the compass variance as described.

Roof Demagnetizing Pattern