OEM auto dimming mirror test

I don't think my OEM auto dimming mirror is working. It's a brand new truck. I turn off the auto light during the night and I don't notice any difference. Headlights seem much brighter than in a manual dim mirror.

How do I test to see if it works. Yes it's under warranty but I don't want to spend the time and travel to the dealer just to test it.

 

Put your finger over the light sensor and see if you notice a difference. Mine has a slight aqua-green tint to it.

 

Yes, I put my finger over the front photocell and shinned a flashlight on the back one to simulate car lights at night. I don't see any difference. I guess I'll just have the dealer look at it next time I'm in.

 

If the green light is not on, the auto-dim function is not on. It has to be on to work.

 

OK. It's working. You don't find this detail in the owner manual. I pulled the truck into my dark garage and left the garage door open so I can see the sunlight outside through the mirror. You have to have the key in the "on" position to test this. I took a flashlight and shined it on the front (facing the windshield) sensor. Because the garage was dark I noticed that the view in the mirror became brighter. I then put my finger over the sensor and noticed it got darker. The back sensor (one you can see) also an effect. When I put my finger over the back one the mirror went bright. I was not sensing a need to dim because there were no "cars" in back of me.

After playing around with it I found the the dimming amount is variable. It's more then just on or off. The darker it is on the sensor the darker the mirror gets. Also when you turn off the key the "darkness" stays where it last was.

The front and back sensors work together. The front detects if it day or night and the back detects if it should do something about it being night.

Front light: mirror bright all the time
Front dark, back dark: mirror does not dim
Front dark, back light: mirror dims variably

In my original post I suspected it not to work because I was used to car lights a few hundred yards back being quite dim on manual flip dimming mirrors. The auto-dimming mirror gets darker as the vehicles in back get closer.

I'm now not as dumb as I look.

 

I was wondering the same thing. Tonight was the 1st time I drove while it was dark.

I felt that the dark rear window affected the auto-dimming. I pulled over, slid open the window and drove for a ways. At this time I did notice the dimming - the road surface was darker as cars approached.

So my question - with the rear window closed does the mirror work as well.

I know that I am overthinking this.

 

Ha ha the whole point of auto dimming is so that you don't get a glare from the cars behind you. If you aren't getting a glare due to tints, then who cares. Either way, you are not getting a glare.

 

You will probably not really notice the auto dimming until the car that is following you pulls into the other lane and shines his lights directly into your side mirror.

You will certainly notice that the side mirrors don't have auto dimming!

 

Every time I start my truck my mirror dims during the day and I always have to hit the auto button now. Is something not working right or should the mirror dim in the day time when it on auto or should it know that it day light out and not dim till night I feel like it never use to be back words.