All 3 heater control wire harnesses overheat and melt switches

SOURCE: old owner chopped blower motor wiring - need pinout for resistor

It might be beneficial to you to go to a scrapyard and take a look at one that hasn't been chopped up! You may even want to buy whatever has been removed while you are there!

SOURCE: fan speed switch continues to melt,wires overheat

Fan motor may be partially failed and is drawing too much power.

SOURCE: my heater has stopped blowing I replaced the

No, it can't be the motor, when it fails it fails for good. Your problem looks more like a bad contact - the normal driving vibrations cut and put back the contact. The selector switch is easy to test: just bypass it (unplug the contact from it, identify the posts and connect the positive and a speed post with a small piece of wire - don't forget to insulate it to prevent shorts while testing), the fan should run at a constant speed continuously. If after testing you find out that the switch is good then you will have to test every single connector and wire to and from the fan/heater assembly - one of them is loose.

SOURCE: 2002 Jeep with a melted

it is very common for the heater resistor to produce heat and create the problem you are stating. It is caused from poor connections and then in turn create more heat and melt connector. The fix is to replace the connector like your stating....BUT most important, make sure connections get soldiered. Also make note, when plugging in, make sure connection is fully seated. Check for any damage to matting pins, signs of black must be cleaned, using small piece of sand paper or small file. If you have, apply some dielectric grease to pins prior to installing, it also helps reduce heat and keeps out moisture.

hope this helps, good luck and feel free to ask and more questions but responding to this thread

Jay