Maybe one of the 3800 guys can help me out here regarding alternator wiring. I have a 3800 II sc out of a Buick Riv. I have the Riv alternator which has a 3 wire connector containing red L, grey F, light blue S. (there is also a P but there is no wire there)The S wire is a tiny bit of a heavier gauge. I have a harness made by Fieroflyer. If he is around maybe he can chime in. The harness has 2 wires red and orange running to a connector. My problem here is how do I wire in the Riv 3 wire alt into the harness containing 2 wires? I really do not feel like trying to find the hardware to mount a GTP alt in the place of the larger Riv one. Can I just splice the 3 wire connector onto the 2 wire harness leaving out one of the wires originally in place for that alt? If so what wire do I not need. Thanks

This might help

Terminal S goes to Battery (+).

Terminal L goes to the brown wire coming off terminal B3 of the Fiero's C500 connector.

The other terminals on this 4-wire connector do not need to be hooked up to anything.

Hooking it up this way will result in it not being under computer control (but it doesn't need to be).

[This message has been edited by fierofan25 (edited 05-30-2012).]

NO

S - Sense - +12v (unswitched battery)
L - Lamp - Connects to the brown wire (If you want to not use the 3800s PCM to control the alternator)
P - Phase - can connect to a device like an external tach
F - Field - Allows the PCM to monitor the field windings of the alternator.

DO NOT CONNECT THE BROWN WIRE TO THE F TERMINAL!

What you should do -

Connect the Red wire of FieroFlyer's harness to the L terminal (The PCM controls the alternator via that terminal)
Connect the Orange wire to the S terninal

Thanks phonedawgz for the clear explanation. Exactly what I needed.

I fixed my mistake,Been working midnight's.LOL

My alt connector has 3 wires: [Orange, Green, Red, empty space]. They're not labeled like anything I can find online. Where do they go? Thanks.

And your alternator does not have an external fan between the pulley and the alternator? Then you have a CS130D

Red - To the PCM

Orange - Optional, but I have been hooking them up anyways - Runts to unswitched +12v. I tie it to where I get power from the power distribution post to supply to the PCM. I have both the S2 PCM and the alternator on a 10A fuse. People think I miswired the plug if there is only the red wire to it.

Gray - Used by some PCMs to know the alternator is turning and how much power the alternator is putting out. Not used with the standard Series 2 PCM swap.

--
You wrote Green, but my guess is you meant Gray.

[This message has been edited by phonedawgz (edited 08-15-2012).]

Only the red wire is mandatory? What is the purpose of the orange wire then, and is it of any benefit to a swap? I'm happy with only one wire on the alternator harness.

Thanks again.

The orange wire is a battery voltage sense wire. The battery sense wire would be needed if there was a significant voltage drop between the battery and the alternator. You might want to keep it if you have a remote battery, however it is not required.