I have an 86 Trans Am but the previous owner seems to have replaced on of my headlight motors with the later 2 wire version. With my car being set up with the 3 wire connection is there a way to make this motor work? I'm assuming the 3rd wire is a ground? Sorry, I'm sure this has been asked a 1000 times but i didn't see an answer

 

Hi knightriderknut, welcome to TGO.

As to your headlights, there were as you likely know two distinct versions of the circuit, the early and the late versions. The early version (your car's native system) was rather archaic, using "limit switches" to indicate to the relays in which position the doors were, and of course the three separate relays to control the motor's movement. The later system did away with the limit switches and three separate relays and used a single solid state module instead. The motors are not interchangeable between the two systems. If you want to keep the original system in your car, you will have to find one of the old three wire motors (no, one of the wires is not a ground). I am including the schematics of both systems so you can see the differences in the motors and their associated circuitry.

Now, my own personal ramblings, , , were this mine, and since I don't at all like the original system, I'd be strongly tempted to pick up a two wire motor for the other side, a new module, and the appropriate pigtails, and convert it to the later (two wire motor) system. There are actually two variants of the later module based system, the one I'm giving you the diagram for (1992) shares the module with the Corvette, so the module still is obtainable (it's not listed as available anywhere for the Firebird, but it is still available for the Vette, go figure)....