Someone asked if there was a way to reprogram the autodimming mirror so that it would activate earlier.  Another question was how does the car know when to switch from daytime running lights (DRL) to the regular headlights.  We'll take a look at how these two features on the Impala know when to activate.


First off, let's examine the autodimming mirror.  The mirror has two light sensors on it.  Here we can see the front sensor.  It is located on the back of the rearview mirror on the driver's side.  This measures the amount of light in front of the car.
This is the second sensor and it measures the amount of light coming from behind the car.  This would normally be headlights from cars behind you which would bounce off the mirror into your eyes.  So if the front sensor reports that it is dark (nighttime) and the rear sensor registers a bright light (headlights from the car behind you) the mirror darkens.  If you want the mirror to darken earlier, a quick (and reversable) fix is to partially block the front sensor.  A small piece of black electrical tape applied across the sensor well to partially block the opening would reduce the amount of light hitting the sensor.  By trial and error, you can adjust the opening to your liking. Note: In this photo, the rear sensor looks like it is lit.  It isn't, that is light reflecting off the sensor.


This is the sensor for the lighting system.  It is located on the dashboard, in the windshield defogging vent on the driver's side.  If this sensor detects light above a set threshold the lighting system goes into daylight mode (bright instrument lights and DRL).  If the ambiant light drops below this limit, the system enters nighttime mode (user-set instrument lights and normal headlights/marker lights).  There is a delay built into the system so the lights don't change when you drive under bridges during the day or under streetlights at night.

I really appreciate the autodimming mirror.  It's nice not to be blinded by other cars.  The autoheadlights can be annoying.  I park in a garage so when I start off, the car thinks it's night and the dash/radio is dim.  It takes some time for the system to switch over.  If I turn the lighting up, when I start the car at night, all the interior lights are now too high.  So I end up fiddling with it all the time or just living with it.