I recently bought a 1989 corvette with 100k miles on it. The seller did mention that the blower motor was not working and that he recently refurbished the AC control module. So I went ahead and bought a new blower motor, however, when I tried testing the new blower motor by plugin it in to the car without installing, it did not run. I went and checked the AC fuse it turns out that the fuse was missing for some reason, I also found two of the same rated 25 A fuses burnt in the car. After replacing the fuses, I tested the connection with a multimeter at the blower motor, when the ignition was on it read 13-12 volts. However, as soon as I turned the engine on and the AC or heater on, the voltage drops to 1.5 V I can't figure out why the blower motor wont engage and if the voltage drop is normal.
That's way too much voltage drop. First thing I do would be to test the blower motor itself using power and ground from a battery. Maybe that's bad. If not, you got a really bad wiring short somewhere between the battery, the switch, the resistor and the motor. Often. It's just a bad blower motor resistor
