Hi,

Does the blower motor run with the switch in the OFF position? If you leave the blower motor switched continually on you may not notice this.

If so I suspect that there is an earth fault on one of the wires connected to either pin 4 or 5 of the resistor.

If not then it may be a faulty blower switch

Here is a the blower circuit for a 2002 Dodge Dakota. Hopefully it is the same for your particular year model.

With a DMM (Digital Multimeter - Ohmmeter function) remove the blower resistor and measure the resistance readings on the blower resistor module between pin 2 and pin 1 (should read 0 Ohms) then between pin 1 and pin 3 then 3 & 4 then 4 & 5 and see what they are reading to find out which one has failed.

I suspect that there will be no reading between pins 1 & 3. This is because this is the resistor which carries all the current when the switch is in positions low thru med 2.

However I am suggesting that if for example you had an wiring earth fault on pin 4 and the switch was on Med 2 then not only would you have the normal current flowing through the resistor connected between pins 1 & 3 BUT you would also have more current because of the circuit path available thru pin 4 (which shouldn't be there). This scenario is the same for pin 5 with the Med 1 position.

It could also be an internal blower switch fault and that there is a short circuit connection between either the low and Med 1 setting or between the Med 1 and Med 2 setting. Hi should not affect it as it is a short circuit through the resistor anyway. With the plug disconnected from the resistor measure back toward the switch between the wires for pin 3 & 4 (light blue and light green/yellow) and 4 & 5 (light green/yellow and tan). and rotate the switch. There should never be a reading between the wires with the switch in any position.

Hopefully I have not confused you with all this.