View Full Version : Weird Auto Dimmer problem. Really freaky.
So i'll keep this short and sweet.
Recently my auto dimmer has been acting up. I thought the light sensor was going bad since it would work intermediately. Dimming intermediately really pissed me off I learned this week.
I have a covered parking space so i usually switch my head lights off before turning off the car. So for testing purposes i shined a flash light at the sensor and it dimmed. Thought all was good, shut the car and off to home.
Today it started working intermediately again and i did the same thing, turned off headlights and shined a flash light to make sure it was still working.
Then it hit me! The auto dimmer only works when the headlights are off!! WTF! Mirror has a blue tint with a flash light then turns normal as soon as i turn on the headlights.
This doesn't explain the intermediate operation of the dimmer in the last few days, so i take the car out with the headlights on. Auto dimmer not working, ok i knew that. Then onto DC 395/295 for highbeam heavan. The dimmer started to work intermediately once I got onto highway traffic. Then it hit me again, the dimmer works with the headlights on and when i suppress the brakes. Whoa, I don't even know how to approach this problem!
I really hope someone here has a similar problem and can help.
Summary:
Dimmer works If headlights off
Dimmer works with headlights on and brakes are suppressed
No one? Google search only showed one other person with the same issue, but no one responded to his post either.
I think this has something to do with the tail lights is works through the brake pedal.
audihere06
11-05-2014, 11:14 PM
I've heard some crazy shit like this with jettas but not Audi's. Either something is shorted or your car has taken up witchcraft. Message the other guy and see if he figured it out.
It was a a really old thread on Audiworld. Think they guy probably threw his fist through the rearview mirror by now.
Witchcraft you say? Wonder if the new ross tech devices can detect that.
audihere06
11-06-2014, 10:37 AM
Well some tunes are infused with voodoo magic, so who knows. If your lucky it could just need a reset or reflash. Have you taken it anywhere?
Haven't taken it anywhere. Before this started i was getting bulb out errors which included brake and left turn signal.
I am going to change out all the bulbs and see if this works. Just noticed my diver side tail light is very dim when on and works fine with the brakes is engaged. The rear view mirror might be confused from this signal.
I always thought the rearview mirrored monitored light coming in from the windshield and rear view mirror and was independent of headlights and taillights. Guess i'll find out in a hour or so and report back the results tonight.
I am in the middle of auto dim retrofit so my post might not be that helpful, but here is what I know about it.
I am assuming you have factory installed auto dim mirror.
Do this test outside when its dark. Parking garage is not the best place to test the auto dim mirror.
1. There are two light sensors, one behind the mirror and one in front.
Put a black tape on the square hole that faces the front windshield, and shine a flash light on the mirror part. This should dim the mirror and un-dim it when you remove the flash light.
2. If the interior lights are ON, the auto dim will not work. So make sure the doors are closed and all the interior lights are off.
3. If the car is in reverse, auto dim will not work.
4. You can reset the mirror. If you have the mirror with a button in the front, press and hold it for some time. That should turn off the mirror completely including the compass. Turn it ON again after sometime by pressing the button. If your mirror doesn't have a button, there should be a small hole behind the mirror (surface that faces the windshield). You can use a pen or small phillips screw driver in that hole to turn the mirror OFF I believe.
5. If you have access to VCDS, you can run a test on J519 (CCEM) and see if its sending correct signals to the mirror.
6. Get a friend with an auto dim mirror, and swap to test if the mirror itself is broken.
- Do you have rain sensor installed? If yes, do the automatic wipers work when you splash the windscreen in front of the sensor?
- Do you have coming home/ leaving home lights enabled? If yes, do they work?
I ask because the functionality of these depend on the signals coming from the sensor on the mirror.
Edit: And do you have a tint strip on the windshield that may be interfering with the sensors?
audihere06
11-07-2014, 12:17 PM
My auto dim works in reverse.
^ As far as I know, the mirror shouldn't dim when put in reverse. Or let's say if it were in dim state then it should un-dim when the car is on reverse.
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audihere06
11-07-2014, 12:25 PM
I wish it did that but usually I have to turn it off to see.
Is it OEM or did you retrofit it? And what year is your A4?
Their is a certain wire that you need to connect to CCEM (J519) to get the un-dim on reverse functionality. But if it was factory installed, then the wire should already be there. Not too difficult though.
audihere06
11-07-2014, 01:30 PM
Mines OEM and a 2006
^ I will check which wire and and let you know. I am going to write a detail DIY on full auto dim retrofit. Hopefully, I will get that functionality covered as well. I would hate to turn off the auto dimmer every time I put the car in reverse.
ok guys i figured it out.
Changing out the tail light bulb fixed it all.
What gave this way was auto dimming operating when i engaged the brakes.
My driver side tail light was going out and kinda dim, but did not produce a bulb out error. So i didn't think this was the issue.
I think the auto dimmer only works if the tail lights are on. Since the tails were dim, it probably wasn't sending out the correct resistance to let the dimmer know it was time to operate. When i engaged the brake, the bulb worked fine and send the signal to dim.
This is just a theory, but it seems there are a little more conditions that we didn't know about to operate the auto dimmer.