Auto darkening mirrors

erubus · #1 20th October 2017, 03:58 PM

Hi guys. now that my starting issues are resolved its time to get down to fixing the other annoying niggles that the car has.

One of these is that the driver's side auto darkening mirror very often auto darkens - and stays dark, meanwhile the rear view mirror stops working altogether. The passenger side is not affected due to being a non - darkening replacement.

The problem always occurs on start-up and as far as I can make out can only be fixed by pulling the battery for a few seconds. I originally thought it was due to the car struggling to start and causing various electrical glitches but it has since done it with the fixed starting.

So for the questions: Has anyone experienced this before/know what causes it and know how to stop it happening or even how to reset them without pulling the battery?

I'm slightly suspicious of the power management module. It doesnt communicate with my crappy copy of VCDS so I cant see if it has any faults logged. It seems the auto darkening mirrors are expensive to replace and there is something of a waiting list for them! I would really like to replace both the wing mirrors though as I constantly get dazzled by the passenger side one and the liquid inside the drivers side one leaves a little to be desired.

gill

HPsauce · #2 20th October 2017, 05:22 PM

I'd disconnect the drivers side one and see how the system behaves; it could have a fault that is throwing the control module off?

erubus · #3 21st October 2017, 09:31 AM

Its worth a try. I should have mentioned that there are no faults logged on VCDS fo the mirrors. when the drivers side mirror goes dark the rear view fails to go dark.

My suspicion is that it is some sort of voltage spike type fault due to it only happening when the engine is starting, but that is purely a suspicion. Its one of those faults that is a niggle, but an annoying niggle all the same haha.

HPsauce · #4 21st October 2017, 05:29 PM

How clever are the dimming mirrors in a D3? I suspect the answer is "not in the least" but I don't know the setup.

Most systems are remarkably simple - a sensor (usually two, one for daylight, the other for detecting headlights behind) in the interior mirror and a very simple control circuit that varies a voltage to all 3 mirror glasses (interior, left and right) to control the dimming.

So just replacing the interior mirror unit may fix it. £26.59 from our sponsors: http://www.ebay.co.uk/itm/Audi-A8-D3...-/170928366722

I'm sure other colours are also available if that doesn't match.

Of course, as you probably know, the exterior mirror glass is in a separate price category.

erubus · #5 22nd October 2017, 09:08 AM

Are the interior mirrors the same for the D2 and the D3? They certainly look the same. I have a D2 one sitting around already.

I will wait and see if it continues doing it before I start taking bits apart. It has only done it the once since the starting problem was sorted.

erubus · #6 19th November 2017, 02:06 PM

Ok, so this is getting annoying now. It is consistently below freezing every morning up here now. This takes more juice from the battery to start it which seems to be what is causing the fault with the mirrors. I will try changing the rear view mirror and see if that makes any difference seeing as I have one (D2 though).

I wonder if the keyless entry is draining the battery overnight enough to cause the problem. I wonder if the countless jump starts and battery drains from the hot start issue I used to have has damaged the circuitry?? There are so many variables for what should be a fairly simple system its bordering on alarming!