I had this same problem in my 94, even with new parts. This is from old worn parts and deteriation of wiring. part of the problem is the amp draw from the blower motor is drawing through the switch, those switches are not design for high load.
i burned up two switches before i installed relays. Like black, burned, melted, fire waiting to happen.
you will need 4 relays and relay pigtails( look under ac compressor clutch relay @ parts store)
Low speed is wired directly to the resistor pack from the ac seloctor switch, M1, M2 and high are controlled by the fan selector switch. so you have four wires.
the reistor pack is located in the passenger foot well, behind a sheild. it has 5 wires. the fith wire is the output wire to the blower motor.
i belive you should have a yellow with black/brown, a blue, a brown, and two greens. don't quote me.
yellow is Low.
Green one is high
green two is Output.
Wire the relays as such. Pins 30 and 87 are the load side. 85 and 86 are the coil(switching) side.
the extra green wire is what runs directly to the blower motor, this must remain conector to the resistor pack.
wire all pin 30's to fused power. Wire all 86's to ground. cut the wires at the blower motor resistor pack. Wire the side from the fan switch to pin 85. wire the side from the resistor pack to pin's 87. pin 85 and 87 must be the same color. I mounted my relays in the passenger kick panel.
In order for the fan to still function on all speeds the power must still run through the resistor pack.
This will remove all load from the fan switch, and prevent the switch from burning again.
This is a factory problem, jeep should have installed a blower motor relay. the motors can draw 25-30 amps.
