From ’76-’06, all of the blower motor resistors were held in place with two bolts. From ’76-’96, they can be found here in the upper plenum. From ’97-’01, the resistor is in the bottom of the heater box, above the passenger’s feet and often hidden with a plastic panel. The ’02-’06 models have the resistor accessible on the front of the heater box between the box and the dashboard. To test, find the wire that delivers 12 volts to the resistor, unplug the resistor, and then use an ohmmeter to test between that terminal and the others. The exact numbers don’t matter too much, but if you find an open short, your resistor is bad.