The blower motor resistor on your Chevrolet Blazer is located in the heater box under the right (passenger) side of the dash. The main part of the resistor is inside the heater box. All you will see is the electrical connector and the wires going to the blower motor. The resistor block is held in with two small screws, one of them can be a bit hard to get to. You can remove the trim panel under the right side of the dash and have a look!