jr'sAudiA6

After viewing your video I'm of the opinion that indeed this abnormal and for sure you have some kind of problem with your vehicle. Hopefully it may be just a faulty light sensor at least that is what it seems like to me based on your video.

The suggestion to check the HUD in a lower light environment, when this happens, is a very good suggestion as this further adds credence to the idea of a faulty light sensor if the HUD is visible under a low light environment.

Good luck on getting this problem solved.

younger64

I left the car outside this weekend, and when the car started exhibiting the strange behvaior (no HUD visible, headlights on when bright outside), I pulled it inside and lo and behold I could see a very faint HUD display. It did require almost complete darkness for the HUD to be visible. So it sounds like a light sensor that fails when warm and sends a signal that it is dark outside could be the cause. Not sure how much work it is to replace that light sensor (believe it is the one up behind the rear view mirror that also senses rain), but I will discuss with the dealer.

jr'sAudiA6

Hopefully with latest info you get this issue resolved ASAP. Good luck!!!

qqq1970

The symptoms point to faulty light sensor.

younger64

Just got the car back after being at the Dealer's for 2 days. Great that I had a very nice 2013 Q5 hybrid as a loaner, not so great that my car remains unfixed. I mentioned the possibility that the issue might be related to the light sensor, but no progress so far. The service writer told me that the issue has now been escalated from the Audi Tech Line to Audi Product support and I should expect a call in the next few days. He said the youtube video was a big help is verifying the nature of the issue. I remain patient while they try to figure this one out.

jr'sAudiA6

I think because of the high degree of technology used in a lot of todays high end vehicles it overwhelms the average auto technician. Todays autos have a bunch subsystems that are tied together thru various types of communication buss's. Many sensors are used to feed these subsystems and if the technician does not have a good system level understanding of your car than they totally rely on provided diagnostic tools to feel their way thru a problem. The problem is these diagnostics tools themselves may not be adequate to address all possible problems.
It is interesting that based on the symptoms of your problem common sense has told several of us that the problem must be with the light sensor that feed these various subsystems.
Oh well, I hope the escalation of the problem up the chain will resolve your problems.

younger64

I have to agree that your assessment is bang on. The behavor of the dealer and the techs do line up with it. There is just so many complex systems that although a problem seems simple to you and me (i.e. must be the light sensor, just throw a meter on it and measure its output when it is misbehaving, then you will know), they need to rule out other possible causes like a software bug or faulty electronic module. It could be that part of my issue is that although the light sensor (or some associated wiring or electronics) appears to be misbehvaing (by communicating it is dark out when it is full direct sunlight) the signal it is giving is still within the acceptable range, so the car is not throwing any codes or errors.

The car just returned from a 2 day trip at the dealer to solve this issue. This makes it 4 trips and 8 days at the dealer total for this problem. I had an opportunity to talk to the head technician this time, which was refreshing, since he clearly had a good grasp of the issue. Although they have been able to reproduce the error, it requires sunny weather, which they didn't have this time. They plan on measuring the sensor and associated modules once the issue occurs. I agreed with them there was no sense in holding my car waiting for sunny weather, so I will wait for the next sunny day and then drive it in for diagnostics once it fails and the HUD disappears and the headlights turn on.

The tech told me if the sensor is faulty, they can replace it without replacing the windshield since the replacement sensor comes with a replacement 'gel pack' to ensure proper contact with the windshield.

As an aside - I asked them to deactivate the auto locks (Where the car locks the doors once you start driving), and the tech told me that they can't at this time. Not a big deal, but I don't understand why some Audis allow this in the MMI (like the 2013 A4 I had for a loaner) and some do not.

gatorguy7

Absolutely agree. My S6 had a check engine light that Audi wasn't able to figure out for a while. They had to bring a specialist for the S6 to eventually figure it out after 2 weeks. We are talking about mechanics who work for Audi and specialize in Audi cars but they still had to bring someone who specialized in a specific model.

younger64

Great news. It looks like the dealer has finally fixed the issue with the HUD and the auto headlights when the car is parked in the sun. It tool a long time (around 2.5 months), 5 trips to the dealer and getting Audi Canada involved, but it appears the issue has been resolved. The dealer did do everything they could, and although they did upload information from the car to Audi Support, ultimately Audi was not able to determine the cause of the problem. The dealer's mechanic was great in that he agreed with me (and other posters in this forum) that the answer was to replace the light / rain sensor up behind the rear view mirror. The sensor was replaced two days ago, and I have not had the issue since, so I am hopeful it is now resolved. I guess what made this repair difficult to diagnose was that the sensor signal was still inside of the valid range, so threw no codes even though it was malfunctioning.

I hope no one else ever has this issue, but if they do hopefully this thread will help them.