Compass: Adjustments
Fig. 3 Variance Settings:
Degausser 6029:
SETTING COMPASS
Variance is the difference between magnetic North and geographic North. To adjust the compass variance set the CMTC to Compass/Temperature mode and press RESET buttons for 5 seconds. The symbol VAR and the current variance zone number will be displayed. Press the STEP button to select the proper variance zone as shown. Press the US/Metric button to save the new variance zone and normal CMTC operation. If both buttons are held for 10 seconds instead 5 seconds the CMTC will set variance to 8 and enter the fast calibration mode.
COMPASS CALIBRATION PROCEDURE (FAST METHOD)
When the compass is subjected to excessive magnetic fields, the CMTC automatically enters a fast calibration mode where is tries to compensate for the large magnetic shifts.
If the compass is inaccurate, appears to be inaccurate and the CAL is not illuminated the fast calibration mode may be manually entered by using the following procedure.
1. Set the CMTC to Compass/Temperature mode and press the reset button for 10 continuous seconds. Manual activation of the fast calibration is generally not required.
2. Compass variance sets to the default of 8 after the fast calibration is manually activated.
3. Complete the compass variance setting procedure by referring to the Compass Variance Procedure in this section
4. Drive the vehicle in three 3600 turns in an area free from large metal objects. If the CAL symbol remains lit after completing this step, the roof panel may need demagnetizing.
DEMAGNETIZING PROCEDURE
A magnetic field can adversely affect the compass. Magnetic interference can magnetize the roof panel. Magnetizing can be caused by placing a permanent magnet in contact with the roof panel. Example:
- Magnetic Base Antenna
- Magnetic screwdriver
- Audio speakers
- Refrigerator magnets
- Pizza Signs
- Bubble gum flasher lights
Removing magnetic interfering objects will usually restore normal compass operation. If the compass display remains blank while the CAL label is illuminated, then the roof panel requires demagnetizing. To demagnetize use Special Tool 6029 for demagnetizing the roof panel. The demagnetizing procedure will demagnetize the roof and mounting screws in the overhead console. It is important that you follow the instructions below exactly. The mounting screws and the mounting brackets around the compass area are steel, and therefore aid in the demagnetizing of the roof panel.
1. Be sure the ignition switch is in the OFF position before you begin the demagnetize procedure.
2. Plug the demagnetizing tool into a standard 110/115 volt AC outlet, keeping the demagnetizing tool at least 12 inches away from the compass area when plugging it in.
3. Slowly approach and contact the console mounting screw with the plastic coated tip of the tool for at least two seconds.
4. With the demagnetizing tool still energized, slowly back it away from the screw until the tip is at least 12 inches from the screw head.
5. Repeat the last step with all the console mounting screws.
6. After you have pulled at least 12 inches from the last screw, remove the demagnetizing tool from inside vehicle and disconnect it from the electrical outlet.
7. Place an 8 1/2 X 11 inch piece of paper length-wise on the roof of vehicle directly above compass. The purpose of the paper is to protect the roof panel from scratches and define the area to be demagnetized.
8. Plug in the demagnetizing tool, keeping it at least two feet away from the compass unit.
9. Slowly approach the center of the roof panel at the windshield with the demagnetizing tool plugged in.
10. Contact the roof panel with the tip of the tool. Using slow sweeping motions of 1/2 inch between sweeps. Move the tool approximately four inches either side of the center line and at least 11 inches back from the windshield.
11. With the demagnetizing tool still energized, slowly back away from the roof panel until the tip is at least two feet from the roof before unplugging the tool.
12. Recalibrate compass, refer to the compass calibration procedure.