Most of the time the auto dimming rear view mirror seems like it doesn't do anything. I've definitely noticed it working before, but far more often it doesn't seem like it works, but I don't know if it's just me or not.
How obvious is it for you guys when the mirror is dimmed or not? Is there a way to test if it's working or not?

 

It's very obvious to me.
Plus you can also increase or decrease the sensitivity setting.
I just leave it on the default normal sensitivity.

 

Are you doing that from the Infotainment or through TechStream?

 

There's a couple of things I've learned about that mirror:

It's got a light sensor in the front to try to modulate the dimming vs the ambient light to make the dimming "just right" for the situation. Well, if you've got a lot of street lights illuminating the road the mirror doesn't really react fast enough for them. I put a piece of 15% tint on mine and it dims it much earlier and it seems to react the way I would want it.

2, the height/angle of the mirror plays a roll with how much light it picks up from the back window and headlights behind you. If you bring the mirror down and adjust the angle to see I'll bet it'll react a little better for you.

2.1, if you take your finger and cover the ambient light sensor, then shine a bright light into the bottom middle of the mirror, you should see it and the side mirrors dim. If not, then you have a problem.

3. There are some folks using those blue-hue headlight bulbs and the mirror doesn't seem to react as strongly against them to block the light. That, and if your rear glass is too dirty (inside or outside) then the light will be scattered and not as strong hitting the sensor... and that'll also mess with you. I think the tint on the front sensor will help with this.

Edit: I decided to go ahead and do this to my mirror with the tint. FYI, it's a 20% sample I used.

 

Just Infotainment only.

 

I don’t know of the settings, but since my car is tinted I had same issue and just covered like 75% of the sensor with a piece of electrical tape and it dims on time like I want.

 

Right now in the twilight of the morning and evening it will now dim the mirrors slightly without a car behind me. Kinda odd to see at that time of day, but at night it works perfect with all headlights from what I see.

 

Looks like 20% tint was just enough. Case in point, top pic is the headlights of Jeep that had way too bright a pair of headlights (either wrong bulbs without reflectors or just a moron with his brights on). Below it is when a car got in front of him and the mirror adjusting to normal.

Definitely worth putting darkening that light sensor lens as before all the light from that jeep's headlights would've been reflected right into the cab