Ok so I have a 2001 a6 2.7t. And when I got the car it had aftermarket headlights. I noticed the driver side hid was noticeably dimmer then the passanger hid. So I had a hid kit from my a4 and put them in to fix the prob. And same thing driver side was still dimmer. so I had another set out of my other a6 and put them in. Same problem. I the switched everything over to the other side to see if it was the hid and it worked fine when I put the driver side hid over the the passanger side. So I am now thinking its a wiring harness or ground issue with the driver side. Any idea on where to start its driving me crazy anu help is appreciated. Ps I took the headlight apart cleaned the lens and properly aimed the headlights already.

 

I need help wuth this. I'm going crazy!

 

I forget if you can plug up the headlights on the opposite sides, but I would try that if you're able to.

If it's still dim while plugged into the passenger side, that would let you know if it's a wiring issue with the internals of the drivers side assembly, or a wiring/grounding issue on the car itself.

 

HID headlights depend on a ballast for each bulb. The ballast converts the car's 14.4 volts to something like 30-40,000 volts to create the plasma discharge in the capsule.

If the ballast is weak or failing, it will provide lower voltage and that will make ANY capsule (wrongly called a bulb) that is plugged into it dimmer.

So if you swap capsules or headlamp assemblies and "this side" is always still dimmer? That's either a bad ballast, or the ballast is not getting full voltage from the car.

You can test the input to each ballast to see if they are both getting 14.4 volts when the car is running, but testing the output will require a voltmeter with something like a 50,000 volt DC range to test it safely. (And that voltage IS dangerous to work with, if you aren't familiar with it.)

 

I have tested it already....that's why I'm confused I have full voltage and I have zero resistance on my ground and no shorts to ground or anything...could there be a prob. With the cutoff plate before the lense? I have not messed with them but could they have been messed up right out of the box?

 

So you're saying you swapped out the complete HID system, ballasts and capsules, from two other cars and the only thing that isn't swapped is the actual headlight assembly, the housing?

And that one of those housings is dimmer than the other, even when everything else is swapped?

Sure, it could be a bad housing. Could be poorly manufactured, could be the metal reflector is "tarnished" or corroded slightly. Could be the blocking plate is out of alignment, or the capsule isn't seated properly. If you can't see or measure any differences, a new set from a better source (Audi from junkyard?) might be the answer.

 

Just a thought. Did you check for battery voltage input to the ballast with the connector plugged in to the lamp assy (lights on obviously)? It is possible to have full static voltage but under load you may have (for example) only 9 volts, 4 volts, or in some cases zero volts, etc. All it takes is to have one strand of wire in the bundle to have 12v static but it won't carry a load. I mean, one strand of the 10 or 15 (or whatever) the wire itself is made of. Also, when checking the input voltage, hook your ground probe to the headlamp ground wire and NOT chassis ground or battery. Same as a poor supply circuit, a poor ground may not show itself except under load but an ohm test may look just fine.
As I said, just an thought.

 

No, the cut-off shield is just there to keep the reflection from the bottom of the projector bowl from blinding oncoming traffic. It could be an issue could be with the projector bowl itself, the reflector portion could have be burnt/scorched overtime -- making it dull and less reflective.