Audi A8 light sensor failure

[Mark999]

The light sensor on my 2003 Audi A8, after failing intermittently, has now stopped working completely. At the same time - and I am guessing the two things are connected - the automatically dipping drivers door mirror is now permanently dipped dark which means at night you can't see anything in it. (It beats me though, why the default setting for the door mirror wouldn't be 'light' rather than 'dark').

 

Oddly enough, this doesn't seem to effect the auto-dipping rear view mirror which doesn't work but as luck would have it has defaulted to 'light'.

 

When I select the 'auto' headlights position a message appears on the dashboard saying that the 'light sensor is faulty'.   Where is this sensor?  Does it control the rear view mirror and the door mirror dipping function?

 

Thanks,

 

Mark

[James]

Mark, from what I've read I believe it's all related.

 

The sensor is located on your windscreen in front of the rear view mirror.

 

Some people have reported disconnecting the battery for a few minutes will cure the problem though not sure if the problem will resurface.

 

It could also be worth cleaning the contacts on the sensor too.

 

Let us know how you get on  :)

[Mark999]

James - I allowed my battery to get very low - to the point where it wouldn't start - and after I'd charged it again the photoelectric (whatever!) drivers side mirror had gone from dark to light again, just as you suggested. Thanks for that.

 

While I am on the subject of the battery, I have done extensive tests with a multi-meter, but cannot find anything that would account for the fact that my new 110 mah Audi battery loses charge at the rate of 0.6 volts per day if the car isn't used.  Does anyone have any ideas what component might be responsible for such a drain?   I have checked the obvious - boot lights, etc.  There are about 30 tiny lights which illuminate switches all over the inside of the car - is it normal that these should be on day and night?  Mine are.

 

Mark

[James]

Mark - are you sure they're not going off after a period of time? Have you come back to the car after an hour or so to check? This can sometimes happen on some cars.

[Mark999]

James - I can confirm the many switch and control lights never turn off.  It did seem odd to me as why would you want them on when no one was in the car and it was locked - although they also stay on when it's unlocked. The actual instrument lights - speedo and tacho, etc, do turn off with the lights.   I have located the fuse which relates to these tiny control lights and indeed they do turn off when it's removed, but the same fuse is linked to the folding wing mirrors and wing mirror positioning electronics, which I don't really want to lose.

 

Mark