I was looking behind the dash of my 70 elky, and I noticed a melted black with a purple stripe wire coming out of the plug for the fan speed switch or main switch (i don't remember). I was wondering what it goes to because I traced it and it just goes to the fuse box. It's not shown in my wiring diagram manual. I disconnected it because it's melted but everything still works. It's right next to a tan wire and BTW my car has A/C.