RV Mirrors AutoDimming Compass w/Thermometer display.
Each is tested working and includes compass & temperature sensors, mounting button, and wiring pigtail. Easy 2-wire hookup for dimming & compass; 1 more for reverse cancel; 2 more for temperature (5 total).
"If the temperature sensor is short- or open-circuited, the display will read SC or OC, respectively, instead of a temperature. If the temperature drops below 3.3�C (38�F) or is below 3.3�C (38�F) upon power-up, the display will alternate between displaying "ICE" and the temperature. The display will alternate every two seconds for a time of one minute."
Compare to:
http://www.mitocorp.com/flash/nightvisionsaftey_autodimmingmirrors.htm
http://www.aztrucks.com/product.asp?Product=166
For calibration, see this:
If the w/s mirror button is different, see this: