Audi A4 Xenon Failure: Causes & Fixes

Hello,

My friend is having problems with the xenon headlights on his Audi A4 Avant, manufactured in early 2001 (with 284,000 km and an AWX engine).
His driver's side headlight is flickering, and the headlight on the passenger side keeps turning on and off intermittently. The problem occurs only occasionally and with varying intensity.

Sometimes, the headlight only flickers slightly, and then the headlight on the passenger side repeatedly turns on and off. This can sometimes be so extreme that the headlight completely fails. During the failure, the onboard computer also displays a message indicating a "faulty" low beam headlight.

He has already been to Audi, and they are also somewhat puzzled about the problem. Some people suggested replacing the xenon control unit (ECU) and bulbs, while others only wanted to replace the bulbs or the ECU. At one workshop, he was told that there is a new wiring harness available for the Passat from the same production period that is supposed to solve the problem.

He doesn't want to spend several hundred euros just trying things out, so he would like to know ways to narrow down the problem.

A new headlight was installed on the passenger side due to a defective one.

The original D1S bulbs (factory equipment) are installed.

Edit: No new burner was installed.

Does anyone have any idea what the problem might be?
Several people are reporting the same problem in various forums.
It only applies to the 8E (B6/B7) models.

Hello,

I am aware of a problem at Daimler where xenon headlights also failed during operation.

I cannot say to what extent this is comparable, as in this case, some of the lights could not be ignited, and therefore it remained dark.

Von 'flackern' weiss ich im o.g. If nothing.

Does the Audi have a sports suspension?

It is possible for the arc to be 'extinguished' during welding. In such a case, the plasma detaches from the electrode at the point where the current crosses zero. The voltage is too low for an arc to re-establish, and the current flow stops. The light goes out and needs to be reignited.

IDR seems to have forgotten that Xeons are also subject to wear and tear.
The problem becomes more pronounced with increasing wear and tear on the electrodes.

Best regards, Jochen.

Yes, it has the standard sport suspension. The flickering of the xenon headlights has been present since I bought the car (95,000 km). It started as a slight flicker and then became progressively worse until its current state. As far as I know, the flickering also occurs when the car is stationary.


Does the B6 actually have a separate control unit for each headlight, or one for both?

bastion wrote:

Yes, it has the standard sport suspension. The flickering of the xenon headlights has been present since I bought it (95,000 km).

Hi there,

I can't comment on the failure rate, but as Jochen mentioned, the wear and tear is significant, and the "warm start" issue is particularly bad.

I also experienced extreme flickering (Osram headlight bulb, Valeo headlight manufacturer), mainly during light acceleration and with a cold engine. I could almost hear the fuel injection signals. Apparently, my alternator is acting up under load.
As the headlights aged, the problem worsened. At one point, the right headlight emitted a bright blue light (which is often seen in the right headlight due to vibrations). Eventually, new bulbs were installed at 210,000 km, and lo and behold, the flickering was almost gone. I suspect that in older headlights, the ionization of the arc is no longer optimal, which means that the control unit often has to adjust the current during operation --> causing flickering.

Blocking the operating voltage of the headlights with an LC circuit to suppress voltage spikes completely eliminated the flickering for me.

Okay, so we would need to install new burners and then incorporate an LC element?

What is the structure of an LC circuit, and where is it connected?

bastion wrote:

Ah, so we would need to install new burners and then incorporate an LC element? How is an LC element constructed, and where is it connected?

The new burners I installed work better with a Valeo ballast, but I can't say for sure if it's necessary. Based on my experience, the age of the burner is more important for achieving a stable flame.

The LC element consists of an inductor in the supply line followed by a capacitor connected to ground. I have installed a 1 mH inductor and a 470 µF pulse-resistant capacitor.

In addition to the initial warm-up of xenon burners, frequent switching on and off is also detrimental to their lifespan. This impossible operating mode is often caused by continuous headlight circuits or light sensors. In many vehicles, the headlights are switched on when the ignition is turned on, but then turn off again when starting the engine. Those who design systems like this are accepting excessive wear and tear.

Besides that, it might be worth considering replacing such old burners. They have generally lasted a long time, though.

Maybe try swapping the pear bulbs to see if the problem moves along with them!
then you'll know if the light bulb or the starter is defective .

These are D1S bulbs. They have the igniter integrated.

Sorry!
Did you mean the control unit that's located under the headlight?
What kind of problems do Audi A4s sometimes have?
Can you rule out the possibility that one of them is defective?