RS6 (C5) Door Light

[T-elospathic]

Hey all, I'm new. Nice to find a place where people actually know a thing or two about my car.

Introductions aside, my rear driver's side door sensor is messed up. The light will go on and off as I'm driving, but it usually stays on now. It also shows that the door is open on the cluster display.

The thing is, it isn't the switch.. I took it completely apart, and jumpered the wires on the harness even. I tested the switch as well. All either of those produce is a minor brightening of the footwell light when pressed/crossed. Obviously it could be further down the harness, but I doubt it. I think it has to do with the controller, the solid-state that controls the lights, or the wiring where it all converges under the dash.

It probably isn't the solid state, because of how it goes off, however it still could be.. My reasons in asking you all is because I have no idea where the relay is, and I only suspect that the wiring is in the side of the passenger front footwell, if not tucked up under the dash by the driver's footwell.

Anyone had this before? Anyone know where I can find the relays and/or connectors? It's worth a virtual cookie if you get it right..

[T-elospathic]

Bump..this is really driving me insane, does anyone have an idea?

[hahnmgh63]

I would have said the switch in the door too. If you have Vagcom it might point to a problem with the Central locking or convenience module. There is a switch in the door locking mechanism too. Try jumping the door switch and then mess around with the door locking mechanism. The drivers side rear door mechanism with contact switch is 4B0 839 015H, about $200. Original part was a G suffix now superceded to a H suffix so it may be improved?
http://genuineaudiparts.com/partlocator/index.cfm?action=searchCatalogOEM&siteid=214407

[bilko1]

There is a micro switch in the door mech which is operated buy a lever when the door is opened / shut. I had the same problem with my drivers door and had to replace the whole mech as the lever which operates the micro switch has a plastic coating which had worn away. I think you can replace the micro switch if you can find one suitable but it's not available from Audi as a spare part. The whole mech cost me £100 and was quite awkward to fit as you have to make a special tool up to release the key barrel linkage, this should not be a problem for you as it's the rear door and has no barrel.

[T-elospathic]

I took it all apart, the switch is fine and the mechanism is pressing the switch. I'm inclined to believe that it's the controller.. I do have a VAG cable, so I'll see if the controller has thrown an error (I'm sure it says "Intermittent..." something something open circuit, which is never really helpful..). Whether I depress the switch or cross the wires, I get the same odd effect: the footwell light gets brighter, so it seems the controller is getting the signal, it just isn't closing/opening the circuit right. Anyone have a DIY/service manual for replacing the controller, perhaps? Maybe I'll tear it out and see for myself..

P.s. hahnmgh63, love your car. Looks slick.

[T-elospathic]

So (double posting isn't against the rules, is it??) I just got done doing a bit of forensics, and I have concluded that the CCM is definitely not up in the easily accessible dash area. I actually read somewhere that it's under the carpet on the driver's side..which is really discouraging, since my fingers need recovering after clipping errything back into place (I also re-ran my amp+speaker+inverter+sirius wiring so that it goes under the carpet, much nicer). Anyone know if that's the correct location before I get all gung-ho on my carpet?

[bilko1]

I guess it's under your drivers carpet as ours is definately under our passenger carpet, they suffer from water ingress when the plenum drains get blocked.

[T-elospathic]

How convenient.

[T-elospathic]

Well, it wasn't actually that bad to remove. It was located inside a very waterproof box right in front of the driver's seat under the carpet. No need to remove the seat, just put it as far back and tilt the front up to make your job easier. Upon investigation, it appears that a diode on the CCM board itself has burnt out. I'm currently preping for surgery to replace it, as I have plenty of spare diodes on hand. If I'm successful, I'll write up a little DUI just in case anyone is ever interested in doing it themselves, instead of buying a whole new module.

Update: Replacing the diode had no effect (that I can tell). When I unplug the tan connector at the far end, the lights will dim and the footwell lights will turn off. The car will also lock and arm the alarm, as well as not show any doors open on the instrument cluster display. Perhaps this goes to a separate module, perhaps the alarm module itself? I'm almost 100% sure it isn't the CCM, as it's turning the lights off as it should. Also, removing individual wires from this tan connector one at a time seems to have no effect. none of the wires go directly to the doors. Next I'll be pulling the security module to investigate further.

[T-elospathic]

FIXED.

The black w/ red stripe wire (the one that, when grounded, indicates that the rear drivers side door is open) couples with another wire that has the same coloring, but goes to the other side of the car on some unknown errand (somehow related to the footwell light in the back), right at the rear corner of the CCM box. This bare metal splint had been grounding out on the chassis, causing the car to think the door was open. I taped it off, and all is well.

[ben916]

FIXED.

The black w/ red stripe wire (the one that, when grounded, indicates that the rear drivers side door is open) couples with another wire that has the same coloring, but goes to the other side of the car on some unknown errand (somehow related to the footwell light in the back), right at the rear corner of the CCM box. This bare metal splint had been grounding out on the chassis, causing the car to think the door was open. I taped it off, and all is well.

Congrats for finding it!
Do you have photos of the procedure?

[SteveKen]

Here are some pictures of the troublesome areas under the driver's seat.

Water ingress leads to a deterioration of the junctions in the body harness. They either just become corroded ans un-connected or ground out as previously mentioned.

Bird's eye view
<img src="http://www.kendrish.com/galleries/S6/wiring/overall.JPG">

Junction that normally causes the DS rear footwell light built into the seat to stay on.
<img src="http://www.kendrish.com/galleries/S6/wiring/B202_sm.JPG">

Wire junctions near the CLU
<img src="http://www.kendrish.com/galleries/S6/wiring/S2_Q11_Q57_sm.JPG">

Intact Junction ("Crimp")
<img src="http://www.kendrish.com/galleries/S6/wiring/good_crimp_sm.JPG">

Don't ask me how I know all this stuff. . .

[T-elospathic]

His second picture where it "T"s off is where the small red stripe black wire from the door junctions with the larger one, and another smaller one that goes into the tan connector on the convenience module, seen in the 2nd to last picture. They're (all 3 wires) the same color scheme.