I have a 1998 Tahoe that i just replaced the fan resistor and a electrical part on back side of fan control **** now i have the fan working,but in the # 1 position no fan and then all the rest turn fan on but low in air volume the last position # 4 is supposed to by pass the resistor and give a full 12 volts to fan motor but it appears it does not we thinking of another relay some where any ideas,thanks.
Is there a diagram of relays for this vehicle for heating and cooling.

 

I have a 99 Escalade(same as Tahoe or Denali) that has a dead fan switch. Been looking at the issue and believe it is the switch . . . again. Apparently, as the motor gets old it just draws too much current and burns the switches out. They are "melted" at the rear of the switch. It is really a cheaply made switch. Don't think GM was anticipating the vehicle lasting more than 5 - 8 years the way they designed the switch. Too bad.
There is a relay that is used when the switch is in # 4 position. On the Escalade it is in or around the glove box. I believe, at #4 switch position, it switches to a circuit that connects to the 12 volt supply directly. Might want to check operation of that relay. The relay should be able to handle the added current draw of the fan motor.

Earth Rider