Heater and Defrost Motor Switch Wiring

On thing your meter told you is that the case of the motor is not grounded. It's near certain that the black wire is the ground, and that the orange and red are the power leads for fast and slow (or slow and fast).

BTW you can be confident that the black wire is the common between the red and the orange wire. I would get a battery or battery charger and some clip leads and test the motor function. You know that the DC resistance is a little less than an ohm, so you can pick a fuse to protect the motor from your testing using Ohms law. One ohm at 12 volts is 12 amps (V=IR wihich can be rearranged to V/R=I) so I would start with a 10 amp fuse. What is the heater fuse in the Jeep circuit diagram. Then starting with the most likely scenario (black to negative, positive to red or orange) test the function of the motor.

Try connecting both red and orange to positive. It seems very unlikely that a single speed motor would have three leads. You just have to find the combination that gives you high and low.

Sorry for the duplication - some of this has been covered earlier. I'm guilty of skimming over the previous posts too quickly, and focusing on the first and last post.

 

Well, I got my daughters digital camera and looked up under the dash to get a pic of my wires and motor. There is no way I can get a pic of it without taking my heat duct hoses off, and they were a pain to get on to begin with. so no pic at this time. I will try to get one though in near future just so there is something to compare the PO,s pics to for future reference. Seems the OP,s motor was determined to be single speed.