I have an 85 trans am that I picked up a serpentine belt system for it. The serpentine system uses a physically smaller sized alternator. My question is the smaller alt has a 4 pin connector where as the old larger alt had a two pin connector and they both have the large +12 volt bolted connection on the rear. Does anybody know how I should wire this alt to make it compatible with my two wire connector on my wiring harness. Any help will be greatly appreciated. Paul

 

Paul, do you know what gen it is or what vehicle it came from. All Delco gens have 4 pins in the receptacle, in most cases only 2 are used. More info would help. Here is a site you can look at pictures of the different ones. www.alternatorparts.com

 

Danno, the pre 86 alternators had a two pin connector which is what I had, now I have a serpentine setup off of an 89 which has a 4 pin connector. I just need to know which two pins in the stock 4 pin stlye correlate to the two pins in the old stock two pin style. Thanks Paul

 

Paul, you are changing from an Si to a CS gen. The older Si units on some models used more pins but they cut them, or it could be age catching up. You will need an AC Delco # PT 1742 plug/pigtail assy available from any GM dealer or Delco distributor. On the new gen you will see if you look close at the receptacle terminals marked P,L,F,S. Looking inside at the male pins one will be wider, that pin gets hooked up to constant 12 even with the key off. 2 pins from the S you will see the L terminal. That is the lamp/turn on line for the gen. That is key controlled, 12 with key on, no volts with key off. Suggest you use a 33 ohm 5 watt resistor in that line. On the old harness if you have one with 12 all the time and one with 12 key controlled all you have to do is splice into the appropriate wires. The pigtail comes with 3M shrink butt connectors. Sorry it took a day to get back, I was putting a CS gen into a 54 Ford pickup a neighbor just restored. Any questions feel free to e-mail me. Dan