I found the problem with my heater fan. There was a factory defect in the wiring. The plug from the harness was poorly made and the two terminals were touching each other inside the plastic causing it to short the circuit and blow out my fuses the second I turned it on.

 

You would think that on an 84 with 274+ thousand miles on it someone would have had this fixed.

You should check and see if the dealer will cover the repair - sounds like recall time to me!