The blower switch on my 70 chevelle keeps burning up and the AC harness wires that connect to the switch are now fried. What causes this????? What is the fix??? Thanks!!!!!!!!!!!!

Burned wires are caused by too high of a current going through the wires. One of the power wires is shorted to ground causing the wire to fry. Time to get a schematic out and see what the burned wires go to, then with a DVM see what wire is shorted to ground. Find the short and you will fix the problem.