w900l,blower fan white wire melted out of the switch,

When a switch goes bad it can cause excessive heat. That heat can transfer to the wires and cause them to have a high level of resistance. Wires like that are usually hard, discolored, and the insulation usually shows signs of over heating. Then when the switch is replaced the wire resistance generates heat and damages the new switch. That portion of wire must also be replaced and be sure you do not have an excessive load-current draw.

 

How does the short pigtail that connects to the 3 speed switch look. If I were you I would change the switch. short pigtail, resistor, and blower motor all at one time. It isn't hard or really expensive if you shop for the parts. The short pigtail will probably need to be bought at KW. Do not reinstall the HVAC control panel after everything is changed. Turn the blower on high. Grasp the sides of the 3 speed switch. If it stays cool you are good to go. If it gets hot you still have a high draw somewhere. After thought. When changing the blower motor spin it and the new one. Is there any difference between the two?

 

That white wire is the ground, check the other end where it connects to the ground stud behind the tach/speedo cluster on the firewall stud, sometimes it comes loose.