So my ac stopped blowing on 1,2,3 but 4 remains working. I read all over that it was the resistor, so ok easy fix, i went through two of them in the past two days, each time after running the car for about an hour or more i smell a burning smell, so leads me to believe it's not the resistor, but what else could it be? Keep in mind, when i install the new resistor each time, the ac blows fine, but till that hour passes, back to no air. I read that you can test the blower motor by a 12v or volt meter, but i dont have either to check, and i dont want to use my existing battery to do so. PLEASE HELP!

 

I also got around to taking a picture of the plug itself, i cant really tell if its burnt or melted...but have you guys take a look at it. Also no salvage yard has these or my mustang, nor does auto zone or discount sell this harness. If thats what i need?

 

Perhaps you're installing the wrong resistor load, or the resistor is touching something else that it shouldn't be touching (hence the burning smell). Resistors can get VERY hot, even when using the correct load...