If thats all thats wrong,just replace the wiring .Make sure you use the same gauge wires,solder and heat shrink each connection,wrap it with plastic conduit and it will be golden.Ive seen a lot worse.Good Luck

I may have the harness you need,at least the correct wiring,pm me and I will send it to you.
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85 300sd SOLD

,85 745i,95 740i,1972 Suburban,1938 International