Refer to the owner's manual and make sure you have the correct zone selected for where you are located. Make sure the compass sensor is mounted in an interior location with the labeled side facing up and the direction arrow facing the front of the vehicle directly inline with the axis of forward travel. Make sure the compass is mounted on a level plane.
If the compass sensor has been or needs to be moved to a new location, you will have to recalibrate the compass after it has been moved. When the compass is being calibrated, as you turn in a circle, it locates the strongest magnetic reading (North) and the weakest magnetic reading (South), which should be 180 degrees apart.
By doing this it can compensate for any magnetic interference caused by the surrounding metal body parts and electronics. IT cannot however compensate for changing magnetic interference such as that caused by a blower motor being turned on or off, or interference from powerful speaker magnets. You should try to mount the compass sensor in a location that is as far away as possible from these changing magnetic interference sources. Usually 3 feet away from most motors and speakers is sufficient.
Make sure the temperature sensor is mounted in a location away from external heat sources. The sensor should be mounted in a location that allows fresh air to blow over it as you drive.
If the temperature display reads -40 degrees F the sensor or the harness has an open connection in it. If the temperature display reads 127 degrees F the sensor or the harness has a short in it.
Check for a loose or bad connection in the 2-wire temperature sensor harness. Verify that the wires are snapped in the 2-pin housing securely, at both ends of the harness, and check for a cut, broken or shorted wire in the harness.
Make sure the harness connectors are tightly plugged into the display at one end and the sensor at the other end.
Check for a loose or bad connection in the 3-wire compass sensor harness. Verify that the wires are snapped in the 3-pin housing securely, at both ends of the harness, and check for a cut, broken or shorted wire in the harness.
Make sure the harness connectors are tightly plugged into the display at one end and the sensor module at the other end.
Make sure you follow the calibration procedure correctly and that after you push the F/C button to start the calibration countdown timer you drive the vehicle in a circle at a speed which allows you to complete 2-4 full circles while the display is counting down from 60 to 0. If the heading (N, NW, W…) is flashing you can not successfully calibrate the compass. You must correct the problem causing the heading to flash before trying to calibrate the compass - see the next question for further assistance.
Make sure that the White wire in the four-pin power connector has been hooked up. Verify with a multi-meter that you have +12 VDC on the White wire when the headlights are on and zero volts when the headlights are off.
Check the connections in the four-pin power connector. Verify with a multi-meter that you +12 VDC Battery (constant) voltage on the Red wire. If your motorhome or trailer has a battery disconnect switch in it, make sure it is turned on.
If the compass is wired to the house batteries and the disconnect switch is turned off the unit will not work. Verify that you have +12VDC ignition (switched) voltage on the Orange wire, and that you have a good chassis ground on the Black wire.