OK, my headlights are fixed, and here's some info for anyone else who finds themselves in my situation, with several days' wait for a new combi switch. This is how you can get your lights working again until a new switch arrives and you get a chance to install it.

Here's the original post with the problem, input from people (including sources for a replacement combination switch), and a couple updates from me during the process:

https://www.audiforums.com/m.asp?m=753226

When I took apart my headlight switch, the lower contact slide piece was melted and there was a plastic "tail" sticking off the left side, which prevented the contact to slide fully to the left of the switch and activate the low beams. This is how it looked when I took it out of the switch housing:



That "tail" sticking off to the right side, off the main body of the part, is what was interfering with the movement of the switch lever - the tail was hitting the side of the housing and preventing the lever from being moved to the second power position, which would activate the headlights. As you can see, the heat that melted it did a number on the body of the contact as well.

I trimmed it off and sanded down the contacts so everything was good and shiny, reassembled everything, and tried it out - no luck. Took it back apart and messed with the slide some more but it was too far gone to salvage. The plastic had melted and sunk the copper pad into the body of the part and jammed up the springs that maintain pressure on the copper piece. Without that, the copper just floats in the plastic mount and won't make contact with the pads on the switch housing that send current out to the lights.

Now, the way the switch works is, when the lights are off, that lower contact is all the way to the right inside the housing (closest to the steering column). When the switch is moved up to the parking light position, the contact slides to the center of the switch and engages a contact which sends power to the parking lights. On the 12-pin connector that plugs into the switch, this power is sent out to the lights through a gray wire (my Bentley manual says it's black and gray, but my test light says it's the gray wire, and there is no black/gray wire in there). When the switch is moved again to the full up position to turn on the headlights, the contact inside slides to the left side of the switch housing, farthest away from the steering column. This allows it to maintain contact with the pad that activates the parking lights, and adds on a contact for the headlights. The current to the headlights is sent out through a solid yellow wire on the 12-pin connector.

What I did, since I had perfect functionality of the parking lights and no function on the headlights, was to use wiretaps on the gray wire and the yellow wire, and jumper them together inside the column. This way, when the parking lights are turned on, it also applies power to the yellow headlight wire and turns on the headlights. I can't run just parking lights alone anymore, but I don't care - I don't ever use that anyhow. Basically I've bypassed the faulty part of the switch and I have full headlight and foglight function now. I will replace the combination switch in time, but for now this works great as an interim fix. If anyone else has a headlight failure due to a melted switch contact, this is a way to get your car back into working order until you can get the new switch. Sorry about the crappy pics - I promise to get a real camera soon. Here's some shots of the jumpered wires. The orientation of the plug harness in the first pic is with me sitting in the driver's seat and looking at the plug the way it is oriented in the column, and just pointing the connector outward toward the door:



To show this picture of the yellow wire, I kept the harness in basically the same position and put the camera below it, aimed upward. There are only two yellow wires in the harness on my 99 2.8 30V, and one has a black stripe to differentiate it. Do not use that one - it's the solid yellow wire that you want - it's basically the lowermost wire on the harness:



The gray parking light wire I tapped into (the only gray wire of any type on the harness) was roughly 16 gauge and is identifiable with a test light - it's near the top of the connector. The yellow wire for the headlights is a bit larger, more like 14 gauge, and is at the bottom of the connector. There's a yellow wire and a yellow/black wire - use the solid yellow wire. The result of all this? Working lights



There is no danger in doing this, since the wires were jumped right by the switch, so downstream, all of the OEM fusing is maintained for circuit protection. When I replace the combi switch with a new one, I will arrange for a real camera to be on hand and will update this with better, more clear photographs. But this absolutely works, and can be used as a temporary (or permanent) fix if your headlight switch fails on you. As long as you have parking lights, you can jumper these wires and regain full headlight and foglight functionality. This can be done temporarily or can be done and left as-is - it pretty much just eliminates the parking lights-only option, and makes that switch position function the same as the full-on headlight switch position. Do as you please with it, but be sure your wiring is solid - don't leave strands of wire poking out of the connectors or the splice taps, or you stand a chance of creating a problem.

That's it - hopefully this will keep someone else from having to park their car until a new combination switch arrives.

 

You sure did earn that fourth star .

 

I have more pics to add to it but I'm having trouble with Imageshack and Streetneeds (one with the pic-source code, and the other with uploading at all). When I get the others to work, I'll add the rest of the pics.

 

sick nasty, thanks bro! Im gonna try this tomorrow morning

 

Shoot me a PM if you have any questions - I'll walk you through it. I want to get inside the dash from below the knee bolster (panel beneath the steering wheel) and locate the wires there, so that the lights can be restored easily on the side of the road if need be, instead of having to remove the steering wheel to do this - it'd make it a much more simple fix. I'll update this thread when I do that.

 

Great fix here! Do you think you can update the link to the missing pic? I've fixed my combi switch before but that was just sanding the plastic piece that melted and sanding the contacts. It worked for about a month but then it broke again. I think this is the next fix I will try. I might try soldering since I haven't used jumpers before.

 

After some coordination with TheDevil (haha), here is what I came up with. I was able to make my switch function but did not want it to FAIL again due to load.

The first drawing is the diagram if your combo switch can not be repaired. This will turn all lights on in the Running lights position with no extra load on the switch.
The second diagram is for those switches that still function and are not ever wanted to be stranded without headlights. This system functions as factory with both switch positions but takes the load off the switch.

The Bosch relay is a 30amp SP/DT available at any auto parts for $12. All wire and connectors can be purchased for around $20 for a grand total of $32. Total time for repair: 45 minutes

Thanks to Jeremy for his input on this subject as he helped me make this happen last weekend!!

So far, after Airbag lights, ABS modules, Failed turbo, Vac leaks and so on, this problem disturbed me the most but was a breaze to repair!!

 

I am new to A4's. Just picked up a super clean 98 with the 2.8. Got the headlight combi switch issue though. Read your great thread about your fix, and wondered if you ever figured out a way to do this under the dash so as not have to remove steering wheel and airbag?

 

ok so this is the stupidest problem i have ever had a car have. i bought my 99 a4 last year 2 months after owning had this problem found a thread and sanded and cleaned it like it said. lasted about a month fried again. bought a new combo switch, lasted me half the summer. then took the new one apart same problem and sanded again. now its too far gone to sand and im forced to either by a new one or do the jumper which is easy enough. but has anyone found a reason to why the switch is actually melting?

 

Yeah - there are no headlight relays in the car, so headlight current is drawn through the switch. It's too much heat and melts the sliders. I'm working on a relay addition to write up for the forum which should solve it once and for all.