Compass/Thermometer - Diagnostic Procedure Revision: Adjustments
Adjustments performed on the compass circuitry include setting the magnetic variation (True North Adjustment) and magnetic compensation (Calibration) of the compass. No adjustments are performed to the thermometer circuitry.Compass
NOTE: The electronic compass senses magnetic North to determine direction. Mostly roads and maps are based on geographic true north, which varies considerably from magnetic north across the country. Components made of ferrous metals (such as iron and steel) and vehicle electrical accessories affect compass readings, by changing the magnetic field.
Compass True North Adjustment
Compass thermometer calibration and vehicle demagnetizing have been performed by the manufacturer. However, the True North Adjustment has not been performed. Vehicle location will determine how accurate the compass is without performing the True North Adjustment. In coastal or mountainous areas the differences between true north and magnetic north vary considerably. Whenever a vehicle is from the manufacturer or whenever a compass is thought to be inaccurate, the first step taken should be to perform the True North Adjustment. The compass True North Adjustment is done using the following procedure:
1. Align vehicle facing north along curb and safely out of traffic flow on a road which is known to run in a true north-south direction. Use a published map to find a true north-south road if necessary.
2. Make sure vehicle is level and that all doors are closed. Also make sure that map lamps in overhead console are off.
3. Place a paperclip, toothpick, or similar tool into the compass recessed button "B" (True North Adjustment) hole and push up gently until display shows "N". Release button.
4. The outside temperature will return to the display when adjustment is complete. The directional heading should show "N".
Calibration Adjustment
Compass Calibration
Because the vehicle's sheet metal magnetism tends to change over time, the compass may lose accuracy and need to be calibrated. This condition is indicated if the True North Adjustment does not correct an inaccurate compass. A compass that is newly installed in a vehicle must also be calibrated.
The compass is calibrated by the following procedure:
1. Find an open area free from steel structures and high voltage power lines.
2. Point vehicle toward magnetic north. Use a precise compass outside and away from vehicle to make sure vehicle is (+/- 4 degrees) aligned to magnetic north.
3. Make sure vehicle is level and that all doors are closed. Also make sure that maplamps in overhead console are off.
4. Place a paperclip, toothpick, or similar tool into the compass recessed button "A" (Magnetic Compensation Adjustment) hole and push up gently. At the same time depress the COMP button with your thumb until display shows "SE tN". Release buttons and wait until display flashes" SE tW".
5. Point vehicle toward magnetic west. Use a precise compass outside and away from vehicle to make sure vehicle is aligned to magnetic west (+/- 4 degrees).
6. Push up gently on the compass recessed button "A" (Magnetic Compensation Adjustment) until display stops flashing and shows "SE tW". Release button.
7. When the outside temperature is displayed, calibration adjustment is finished. The directional heading should show "W".
8. Perform Compass True North Adjustment as previously outlined.
Vehicle Demagnetizing
If the compass is inaccurate after calibration, the vehicle's residual magnetism may be too high and vehicle demagnetizing is necessary. Initially the vehicle's roof is demagnetized to a sufficient magnetic level by the manufacturer. In most cases this is all that is needed during the life of the vehicle. However, if after calibration the compass still is inaccurate, demagnetizing must be performed.
The demagnetizing process requires the use of a demagnetizing coil commonly used by television service technicians to demagnetize television tubes. Demagnetize the vehicle by sweeping across the roof area over the compass with a demagnetizing coil as follows:
NOTE: The demagnetizing procedure must be performed exactly as described. Never turn demagnetizing equipment on or off within three feet of a vehicle's roof or the vehicle may be remagnetized.
1. Standing three or more feet away from vehicle, turn on demagnetizing coil.
NOTE: Whenever the demagnetizing equipment is being operated over the vehicle's roof or within 91 mm (3 feet) of the vehicle, the operator must maintain a constant steady motion. Failure to do so may result in the vehicle being remagnetized.
2. In one continuous motion make four passes over roof of vehicle. The demagnetizer should be held 25 mm (1 inch) or less (but not touching) away from roof surface.
3. After four passes and without stopping motion of demagnetizing coil, pull demagnetizer away from vehicle.
4. When demagnetizer is at least 91 mm (3 feet) away from vehicle, turn it off.
5. Perform the compass calibration procedure as outlined in Adjustments.