There is a large resistor on the engine compartment fire wall behind the passenger side of the dash. It is connected by slip on connectors. Heat and age causes bad connections. You might check there. I had the problem and thought it was the fan. After replacing it I found the resistor, wiggled the wires and found the problem. (groan) I soldered the wires on and have had no problems for some years now on my '96. Good luck.