I'd been looking all over the internet for a solution to this and figured I'd share.

My husband and I own a 2003 Mitsubishi Montero XLS with the RV Meter
(digital compass, clock, ambient air temp, and fuel guage).

Well a couple nights ago, my husband saw that two symptoms were happening:

1) the outside air temp guage stopped working (displays dashes where there's normally a reading)
2) the a/c controls for the climate control weren't displaying on the unit anymore

Well, here was the eventual fix:

Reset the RV Meter using the "System Connection Check" procedure:

NOTE: The RV meter is reset by using the following "system-connection-check" procedure. Use this procedure to reset the RV meter if the connection information is lost, if there are any display errors, or if any RV meter information fails to display.
a. With the key in the OFF position, push and hold the "DISP" button.
b. While continuing to hold down the "DISP" button, turn the ignition switch to ACC position. Keep holding the "DISP" button until you hear a beep tone which will last for about 10 seconds. You should then see the display shown.
c. Turn the ignition key to the ON position to start the system-connection-check.
d. Wait for approximately 8 seconds. The system will give a beep signal. When the connection is completed, this message will display. "System Connection Check Complete" or something like that..
3. Calibrate the compass as follows:
a. If the compass requires manual calibration, the "Need to calibrate the compass" message will appear on the display for about 7 seconds and the direction indicator will blink. Press the CAL COMP function button within 7 seconds.
b. Confirm this screen then follow the on-screen instructions.
c. Drive the vehicle slowly through a 360°turn in either direction in a safe, open space with no other vehicles or buildings around. This will automatically complete the adjustment, calibrating the compass to the correct azimuth.
d. After driving in circles, the adjustment completes automatically, and this message displays verifying completion of adjustment.

NOTE: ^ The compass can only be adjusted at speeds of less than 2 mph (3 km/h).
^ The display may sometimes show the adjustment completion message when the vehicle begins to turn but then returns to showing the original compass direction. In this case, the compass has not adjusted itself correctly. Make sure to turn the vehicle completely through a 360°turn.

4. Adjust the RV meter compass variance as follows:

NOTE: Compass variance is the difference between the earth's magnetic north and true geographic north. If not adjusted to account for compass variance, the compass could give false readings.

a. Press the "ADJ" button.
b. Find your current geographic location and the correct corresponding zone number on the zone map.
c. Press either the "<"or ">" function button until the correct zone number appears in the display.

NOTE: Pressing either the "<" or ">" function button for more than one second will cause fast forwarding/reversing of the zone numbers.

d. When the compass variance is set, press the "ADJ" button.

5. Check the RV meter outside temperature display. The outside temperature should display correctly.

a. If the outside temperature continues to display incorrectly, follow the RV meter troubleshooting steps in Group 54A of the appropriate service manual.

However I didn't find this above fix until after i'd tried just disconnecting the Neg battery terminal for few minutes, which eventually did the same thing.

as a seperate result of disconnecting the Neg terminal to the car.. i was getting a new symptom:

my M-ASTC Off light wouldn't go off and continued to stay lit after turning the vehicle on, after digging through the manual I found out the light will stay on until some steering feature is recalibrated when the system gets power again. So unlike disassembling the dash to look at the switch like I did unsuccessfully, all you have to do is drive in a straight line at 25 mph for about a street length to get the traction control off light to turn off and your ASC toggle switch to operate again.

If you're like us, we're pretty much trying to avoid the dealership at all costs because that simple reset i'm sure would've put us back a few hundred $$ plus time to get there on the other side of town etc.. hope this helps someone out there..

K