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This is for an 1989 S4. I pulled the CE panel as the first step to figuring out some electrical gremlins and found this burnt wire. It is on the "F" connector number 5 (I think the wiring diagram says 15). The wire on the back side of the CE panel from here to the window relay was also burnt. The wiring diagram is hard to read (bad scan) but I wanted to confirm that this wire goes to one of the door switches like I think. Unfortunately it disappears into the wiring loom pretty quickly so physically tracing it is difficult. Other than this wire, everything else on the CE panel looks good and no corrosion.
Ugh, the scans for the wiring diagrams are really not great for the '89. However, if I'm reading it right, the wire from F15 goes to the left and right door contacts, as well as somewhere referenced by O23, but I don't see a reference to M5 there, so ?.
To see if there was any commonality, I took a look at the '88 wiring diagram and that looks like a much better/clearer scan. In this particular case, those wiring traces look to be the same. That was not the case for the '90, which also has a clearer scan.
Ultimately, these are all grounds for various devices to maybe spend some time with sandpaper and DeOxit to fix the root cause (you may already be on this).
If the wire is melted along its length as far as you can see, chances it got hot enough to melt additional wires in the bundle leading back to its origin. That happened to me when I had a short in the hazard flasher switch. Had to open up the bundle its entire length, remove all the burnt wiring and replace. If you don't see that kind of damage and don't want to open up the harness the entire length, just bypass the melted wire and string a new replacement from end to end and tape or zip tie it to the main harness.
Could it go to the door pin switch that turns on the lights or to the door or hatch lights themselves? If someone put the 3 wires on the door and hatch lights incorrectly the same wire need to be on the same terminal in each light) and the put one of the power wires on one of the ground terminals they could have created a short through the system like that.
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Burnt Wire
