05 AV Outside mirror auto dim

I just purchased a 2005 avalanche and the drivers side outside mirror won't auto dim. If I turn on the interior lights the mirror will dim. Would anyone know if and where the sensor would be located?

Does the inside rear view mirror dim? The automatic mirror dimming system is controlled by the inside rear view mirror. Check to make sure the green light on the front of the mirror to the left of the buttons is lit. This means the inside and (if equipped) outside rear view mirrors will dim when the conditions are met. If the green light is not on, press and hold the button that turns on the compass and temp display for 6 seconds. A momentary press will only turn the compass and temp display off and on. Holding it down will turn on and off the dimming feature (indicated by the green light). The service manual did not indicate anything about the interior lights having to do anything with the dimming mirrors, just might be a coincidence or illusion. Also, check the owners manual, if you have one. It might explain clearer that I was able to. Hope this helps.

Thank You for your reply. My 02 Avalanche would auto dim as a vehicle was passing. On my 05 it doesn't. I have found a sensor on the rearview of the 05, and if I turn on the inside lights the outside mirror will dim. If I put my finger over the sensor the outside mirror goes back to normal. It will not dim as cars pass. Both the 02 and 05 have factory tinted back windows. I guess I am wondering if there is an outside sensor.

It does, I'll copy and paste the part of the manual that describes it.



[The inside rearview mirror uses 2 photocell sensors. One sensor is the headlight sensor, located on the face side of the mirror. The headlight sensor is used to determine light conditions present at the mirror face. The other sensor is the ambient light sensor, located on the rear of the mirror or windshield side. The ambient light sensor is used to determine the exterior light conditions. With a low exterior light condition detected, and a high light condition from behind of the car, at the headlight sensor, the inside rearview mirror will automatically darken the face of the mirror.
In the daytime, the mirror is in a normal state because of the high exterior light condition that is indicated by the ambient light sensor. With the gear selector lever in the REVERSE position, backup lamp supply voltage is supplied as an input to the inside rearview mirror. The mirror monitors this input to disable the automatic day-night feature. This allows the driver to see objects in the mirror clearly when backing up, even during the night.]




The outside mirrors just use the information provided by the inside mirror and then take action based on what the inside mirror decides to do. Hope this helps.