View Full Version : HID headlight flickering issue

07-08-2008, 09:42 AM
Hey guys, hope someone can help - I recently purchased a used set of 2-piece Depo headlights with McCulloch 6000k HID kit from another AZer. They have been working great up until a few weeks ago. Now, each light will flicker every now and then (not all the time and not always the same headlight) and sometimes go out completely. A quick switch off and on of the headlight stalk while I'm driving and it comes back on. At first I thought the flickering was due to bumps in the road, but then realized it was happening regardless of road bumps. When I installed the headlights, I left the ballasts hanging loosely and thought this might be the reason, but I have since zip-tied them against the back of the HID units and it's still happening. My inital thoughts are that the flickering could be a ballast issue, but what are the chances of both ballasts going at the same time? It seems to happen equally to both headlights randomly, but I'd say slightly more on the driver's side. One time both went out together, so this has me questioning the ballast idea. Oh, and also, only the driver's side high-beam works as well, despite changing bulbs and complete headlight assemblies.

I should mention that I do have other minor electrical gremlins which I'm currently trying to get to the bottom of which does include a very recent cruise control that only works when it wants to and can suddenly disengage at speed and high-beam that no longer works when the stalk is pushed forward - only when held back, depsite being blasted out with contact cleaner. This is probably the high-beam/cruise control switch, as I'm pretty sure it's one unit behind the steering wheel. Other problems inlcude the alarm going off on it's own, climate control backlights flickering, etc. - but big surprise there with these cars! Anyway, I only mention these latter issues in case someone thinks they may be related to my headlight flickering issue.

Sorry about all the info, but I'm not very good with electrical, but I do know that the more info given in these situations, the better. Not sure where else to post this, but since it has to do with my '96 A4Q 12v, I decided to post it here... Thanks for reading...

07-08-2008, 09:58 AM
i think your ballasts are going bad. it happened to mine too, but mine were 5 yrs old when i got rid of them

07-08-2008, 11:47 AM
Might be the bulbs reaching the end of their life.

Info here:

07-08-2008, 03:55 PM
My VVME's did this in the summer and sometimes wouldn't ignite at all.
I first thought it was bad ballasts, but i tested a theory and ran a wire directly from the ballast to the battery. what do you know it no longer flickered.
So i relayed the power to the battery and haven't had an issue since.
Been 2 years now.


07-08-2008, 08:20 PM
How did you "relay to battery"? I am having the same issue and my mechanic is stumped.

07-08-2008, 08:27 PM
Yes - please explain. Are you saying there is nothing wrong with the ballasts, just the power coming to them via the normal lighting wiring harness? Is this why wiring directly to the battery fixes it? Sorry, I'm mechanically-inclined, but awful with electrical.

07-08-2008, 10:21 PM
had the same problem with the flickering lights...would happen when going over bumps and then just stopped working..

the first time a blew a fuse...worked for a few months and did the same thing..so i then found that my fuse was not attached to anything and was always bouncing around so i strapped it down...secured the fuse and its been fine ever since..

07-09-2008, 01:08 PM
Relays work in a fashion that the switch will still turn it on but it uses the voltage directly from the battery versus drawing through the switch.


07-09-2008, 01:37 PM
x2 on the relay, having one should fix your problem.

03-05-2010, 10:21 AM
hey guys i can't find a write up on the fix. could someone help me out? my lights are starting to flicker and don't want to be left in the dark.

03-05-2010, 10:44 AM
hey guys i can't find a write up on the fix. could someone help me out? my lights are starting to flicker and don't want to be left in the dark.

Well, if they're just "starting" to flicker as you state and have worked well up until now, it's probably the ballasts or the bulbs themselves starting to go bad. A relay or even a set of capicitors will help if the issue is like mine was - unstable voltage which happend from the minute I made the upgrade. Our older B5s weren't designed for HIDs and these lighting systems require much more stable voltage than regular halogens and this is why mine were flickering. Added two in-line capacitors between the car's original headlight wiring and the ballasts and they regulate the voltage perfectly. Total cost: $7. Try searching for "headlight capacitors" or something like that and you'll find a post with pics of what I'm talking about. The caps were 4700uf (micro farads) and 35v. Hope this helps. Relays kind of do the same thing, but pull from the battery which is DC and not AC (alternating current) from the car's electrical system.

03-06-2010, 12:11 PM
Here's a relay harness:


03-06-2010, 11:10 PM
thanks guys. i think dan might be right. i have stockers so it might be going out.
i'm gonna try to see if anything is loose first, because my buddies b6 stock xenons are still going strong.