The interior rear view mirror has temperature and compass displays, but only work for a short time at start- up.I have tried unplugging the harness on the back of the mirror and cleaning contacts. It`s like something overheats, or times out after 5 minutes or so. Can`t see or find any loose wires at the connection to the harness.

There is help in the link. The general consensus is if neither work, you need a new mirror.

https://www.google.com/search?q=2015+GMC+ACADIA.+Compass+and+temperature+won%27t+work+in+my+rear+view+mirror

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For optimum calibration, drive to an open, level location away from large metallic objects or structures such as bridges, steel buildings, etc. Disable aftermarket electronic accessories and switch off all non essential electrical accessories (heated rear window, heater fan, A/C, map lamps and wipers) and make sure all doors are closed. Start the vehicle. NOTE: The vehicle remains in the CAL mode until the compass has been successfully calibrated. NOTE: While holding the Front Controls Interface Module (FCIM) 7 and 9 buttons down, the compass display first enters the ZONE setting mode (after 5 seconds) and then after another 5 seconds (approximately 10 seconds total), the compass display enters the CAL mode. Press and hold (for approximately 10 seconds) the FCIM 7 and 9 buttons until the CAL indicator appears in the display, then release the buttons. NOTE: If the CAL indicator does not turn off after the vehicle is driven in a circle at least 5 times, repeat the procedure. Drive the vehicle slowly at less than 5 km/h (3 mph) in a continuous circle until the CAL indicator disappears from the display and the compass heading is shown. If the CAL message does not turn off after driving in a circle at least 5 times (and the procedure has been repeated at least once), install a new compass module (integral to the interior rear view mirror). For additional information, refer to Interior Rear View Mirror.

u don't have ample wiring for compass

Does the compass work when the temperature goes out? If the compass still works then chances are that the ambient temp sensor is defective. Also, could be wiring to the sensor. If the compass goes out with the temperature then chances are the mirror itself is defective. Cheapest most common problem is the ambient temp sensor. It's behind the grill by the condenser at the front of the vehicle.

Calibrate the compass built into the upper-right corner of the rearview mirror by holding the compass button (an "N" with two crossing lines) until your zone number appears. Determine your zone number by looking at the map in the owner's manual. Press the compass button until a "C" appears. Then drive in a circle three times at 5 mph or less in an uncongested area. The compass will automatically orient as a result of the circling.

Read more : http://www.ehow.com/how_5927729_reprogram-avalon-after-battery-change.html

u might have to do that with the mirror but the air bag thing i would have a mechanic take a look at it but i think the air bag computer system is failing

Have your resolved the issue stated above. I have been having the same problem. Now my display has stopped working completely.

what could be the problem,its was working just fine.

you could always try unplugging the battery for about ten minutes to see if that resets it. make sure you have the code for the stereo first if it requires one.

Fuse no. 10 (7.5 amp) in the interior (dash) fuse panel.