Lason

iTrader: (1)

OK from everything I have read on here, on a F-body alternator pin B on the 4 wire plug should have a 12v source with a 470ohm 1/2 watt resistor inline in order to "turn on" the alternator. Well I tried that and it didnt work. Got a new alternator same thing. So last night in frustration I decided to leave the wire and resistor where it was and put 12v to pin C and BINGO! Alternator started charging and the gauge went to 14 volts.

So in my expirience, pin B needs the 12v w/470ohm resistor and pin c needs 12v in order for the alternator to energize.

This was a carb'd setup using a '98 camaro alternator (even though autozone only had one part number for 98-02 f-bodies)

bczee

iTrader: (12)

One differences is that the 98' alternator uses the light/resistor to reduce the voltage down.. the 99+ alternator uses the PCM feed with is already reduced to the correct voltage for pin B on the alternator to energizer..

Lason

iTrader: (1)

yeah but what got me stumped was everyone on here kept saying all you need to do is get 12v to pin B through a resistor which didnt work out for me on two different alternators. I needed to provide 12v to pins b AND c. Im thinking pin C is the field wire?

G-Body

iTrader: (4)

Thats an autozone rebuild for you. They put the voltage regulator for a vett or truck in there. The vettes and trucks use the second wire and it is a field duty signal (IIRC, I`m not sure if thats the exact name they use) Anyway it is just a switched 12v+ wire to terminal C.

Lason

iTrader: (1)

The stock GM Alternator that came on the motor was the same way, hence why I swapped out for a new one. I pulled the motor out of the wrecked car so I know its an F-body alternator. I tested the old one when I got the new one and it tested good but I thought different and just got the new one then figured this out.

G-Body

iTrader: (4)

Hmm, I don`t know how the GM alt would work then, because on the factory f-body harness there is only one wire going to the alt. A single red wire that goes to pin B.

andrew69_04

iTrader: (148)

i've worked on 30+ 99-02 F-body LS1's and they all have 1 red wire from the PCM to pin B on the alternator.

Lason

iTrader: (1)

OK well Im not trying to start a debate. Just giving guys who have the same issues as I did an idea that might help them out. With battery 12v on the rear stud and 12v resisted (8.2v after resistor) to pin B the alternator did not charge. Add 12v to pin C and presto, the gauge jumped to 14.5v. Swapped in the old alternator before I returned it as a core and it worked. Went ahead and kept the new one as the old one was the OEM alternator with 70k miles on it anyway.

Eddie 70

iTrader: (3)

Someone correct me if I am wrong on this. I have an 02 SS Camaro LS1 motor, harness and accessories. I do not need the resistor on the wire going to the B pin. If this is correct, I have to fix my flub.

DCx

iTrader: (12)

my resistors never worked on my pin B. i got frustrated and added a light bulb from an autometer gauge inline and that solved it.

im also running a carbed setup.

LS1MCSS

iTrader: (18)

Leave the resistor in there. Without it, the alternator is living on borrowed time.

S10xGN

iTrader: (11)

This came from S&P's website, looks like it can be wired either way depending on which of the center two terminals are used...

Russ

G-Body

iTrader: (4)

Did you use the self contained wiring in the harness to connect the alternator? or did you wire up the alt on its own?

1991ls13

iTrader: (1)

well since im on silvia and they pointed me here, ill ask.
i have a 240sx ls1 out of a 04 gto and my battery keeps dying, batterys good, alt good, grounds fine. cant figure this out. if anyone knows or can think of a solution place imessage me.

thank you

RHDV8

Have a read here, there seems to be a problem on 2004 gto set-ups for some reason in that there is a constant current draw. This solution worked for one guy but seems not to work for everyone. If you try and it works post up what you did etc....
http://www.v8rx7forum.com/showthread...light=resistor

fmowry

iTrader: (14)

How long does it take to die? What kind of draw are you getting? I stupidly had the white and brown wires switched in my Miata swap and was getting a hug draw. I still think I'm getting the small draw others are after I wired it properly, so I might mess with the solution on the RX7 forum thread.

The 99+ Miata alternator plug is the same as the GTO, but the wiring is switched.

Frank

jsbuickpower

if u test for the parasitic draw weight for the computer to fall asleep before you test other wise you will be seeing a draw from the computer or computers

RHDV8

How long does that take and is there a way of telling when it's asleep?

dtfastbear

I wanted to let those folks who started this thread and then contributed to it that you saved my race weekend!!!

I have an LS1 swapped in to a miata race car. We used a Painless harness to do the swap. That harness has no provision for the alternator, so we were on our own to wire it. My wiring guy wired the "field wire" to 12v on ignition. This worked for the alternator that came with the used engine that I bought. However, I had to replace that one and ordered a "99 camaro" alternator from NAPA. I installed it, and it didn't charge. Took it back to NAPA and they tested it. Yep, bad! They gave me another one, but tested this one first. I installed it, and it didn't charge. I took it back and they tested it - yep, bad! They gave me ANOTHER ONE under warranty (Thanks, NAPA!) and this time I did some research and found this thread. I bought a 22 cent 470 ohm resistor, soldered it in to that field wire and viola - perfect alternator operation.

Thanks, guys!!

Longhaul

I have not yet figured out what is going wrong with my set up (98 LS1 into a 89 Rx7), but this thread has lead me to a potential solution.

If you look at the PCM pin out for the 98 vs the 99, there are quite a few differences. The RED connector pin 15 is the "Alternator Terminal" on a 99 wiring harness and the wire color is also RED.

The PCM pin out for the 98 does not include an "Alternator Terminal". It seems to make the set up immune between a 98 & newer that you need to put +12 switched to one pin and +12 switched through a 470 Ohm resistor to the other.

I hope to try this later today and see what happens.

Wish me luck!