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Photograph wiring before you cut
How-to · Electrical
Every extra wire had a reason, even if that reason was bad.
Photograph:
Battery cables and main grounds
Fuse block and anything hanging off it
Harness through the firewall
Aftermarket stereos, lights, and alarm leftovers
Melted, taped, or butt-connected repairs
Do not pull a harness until you can point to what each large cable does.