LS1 Alternator Hookup

Hi Guys,

I have been lurking around here for about a year now. I am working on my swap, I put an L33 5.3L with harness in my 944. I put f-body accessories on the front. I am to the point where the 5.3L harness has a 3 wire plug for the alternator, and the F-Body has a 4 pin.

Does anyone have any insight? I saw a bunch of people using just a single wire to excite it.

Any help is greatly appreciated.

Thanks,

Andy

By 3 wire do you mean the heavy gauge output wire and a two pin connector? Some of the ECMs had connections to the alternator regulate voltage. I believe if you have a self exciting one, you can forget those connections into the ECM. My 04 GTO is 3 wire, positive output, positive input, and an idiot light connection, which requires voltage to turn the alternator on, do not apply full 12v to it. This has been discussed in a few threads on this board, and in great detail on ls1tech.com.

No the truck alt had one big wire on the back, and 3 wires in a connector that went onto it.

I don't see anything wrong with making it a self exciting one.


Andy

I don't see any issue either! I've only seen the 4 and 2 pin connectors, but I've only seen mine and Skywalker's alternator setups in person. I believe I have read that the blue wire is used on a 3 pin like yours. Grey or white to plus 12v, and the brown is the idiot light, that needs a lower voltage supplied to it.

I wired mine with a pigtail from Painless.

http://www.painlessperformance.com/Manuals/30707.pdf

Rich

F body has 4 pin, but only one wire. That wire goes to the PCM, BUT the PCM does not turn the alternator on and off. There was another brain called the Body Control Module that monitors battery use and sends the on/off signal to the PCM which in turn supplied 5 volts to the B pin of the alternator when charging was needed. For single wire PCM driven alternators you need 12v resisted by 470ohm 1/2 watt resistor inline (about 8.2v after resistor) to pin B and ignition switched 12v to pin C. This means removing wires for A and D from the pigtail.

I went to a truck alternator with 4 pin pigtail for the higher amperage, but this wiring works on all of these alternators up to 2002 as far as I know.


The issue as I see it is how the truck motor PCM talks to the truck alternator. You can buy a 4 pin pigtail for the Fbody alternator that has all 4 wires and splice wires to the harness if you know what each wire supplies or you can take the same 4 pin pigtail and follow the directions above.

Hope that helps.

Marc

Hey Guys I finally figured it out.

First off I was looking at the complete wrong connector, secondly my harness that I purchased had the GBCM (some sort of ground body control module) I found the pinouts on LT1swap and I got a new alternator plug and wired it up. So I just used 2 wires.

Thanks!

I destroyed two alternator regulators using the PCM control wiring.
My alternator shop suggested using a self exciting regulator and only one wire (to the battery)
to avoid this problem. No problems since.

I will keep that in mind. If I blow this one up, I will have to change it.

Some replies and info I've found is a little confusing on the F-body alternator. I'm at the point in my LS1-928 swap where I need to make a decision on which alternator to use.

I have a 99 Camaro SS engine and harness and want to know if a later 5.3 truck alternator plugs right up and doesn't fry things.

Or do I need to just buy a new 99 Camaro alternator and what would be the best way to hook it up to the factory Camaro harness?

Rob,
Stay away from the Computer hook up, use a self exciting regulator module and then it's a one wire hook up to the battery (via starter).
KISS

Forgive my ignorance, what is a self exciting regulator module?

For the swap, should I just use the 2nd diagram here if I use the 99 Camaro alternator?

http://ls1tech.com/forums/conversions-hybrids/779728-thee-alternator-faq-thread.html

For an alternator to work, the field winding has to be "excited" or powered.
Most alternators get a kick from outside sources to start the procedure. A self exciting regulator has the capability of exciting its self from the residual magnetism in the unit. Once the alternator is turning it generates its own excitation voltage. I also have one on my V6 MGB and by watching the voltmeter you can see that when the engine reaches about 1500 rpm the alternator output jumps up to normal voltage. Once excited it remains excited.

I uses a F body Camaro alternator on my 948 and destroyed two regulators by connecting the LS1 harness to the Alternator. Only when the repair shop suggested the one wire solution did the problem go away. Frankly I don't see any reason to allow the computer to control the alternator.

You have to buy a "Self Exciting Regulator Module" for this to work. The module is inside the alternator.

O.K. I see. As I recall on the 948 5.3 2001 Truck alternator I used with the SSP wiring harness just had one wire going from Truck ECM to Alternator pin connection. Would the same truck alternator work with the 99 F-body harness PCM pinout?

I had a SSP harness and had the problem hooking it to the alternator. It would work for a short time and then the regulator would fail.
Take my advice Rob, use a one wire deal (Alternator output to battery) the computer does not need to see the alternator.

I had some other problems with the SSP harness with the fan wiring/sensing , frankly they behaved like they never ever did anything wrong even after I pointed out their mistake and they admitted the guy who made my harness had left them.

So use a truck alternator, install the self-exciter module, and only hook-up large gauge(+) wire to battery, then ignore the Check Engine Light?

Check engine light???
Believe I took the (Porsche) bulb out of mine, no problems with the LS1 light it goes out when the engine starts. Sorry all my documents are in FL so I have no reference to hand.

Find a knowledgeable alternator shop for the module, they may even fit it for you.

The thread on LS1tech is basically right, except on 99 and newer LS motors with the 4 pin weatherpac using a single wire the alternator is not turned on by the PCM. The PCM is a bypass for the BCM (Body Control Module) which tells the PCM when to send 5volts to the alternator. I found out about this because I couldn't get my alternator to charge using the 2002 harness connected to the alternator. It appears as if the Painless harness uses the same principle.

I have a KG3 truck alternator with the 4 pin weatherpac and it works perfectly with the set up described in my post above using two wires.

Apparently, the 98 alternator is a little different, don't know whether it is a 3 pin or 4 pin alternator.

FWIW the 2001 truck alternator uses the 4 pin weatherpac which is why my alternator works with the two wire set up.

Old post, I know.
But on a 98 FBody alternator, is it recommended to just use the big wire to the battery and then wire in the alt wire from the Porsche plug by firewall?
My car has a 3 wire plug on the SSP harness I purchased that goes back to the PCM. Think I should leave it unplugged?

Somewhere in time I posted the saga of hooking up a F body alternator. I originally hooked up to the PCM and blew two regulators in a row. My Alternator shop suggested fitting a self exciting regulator module in the alt and then you only need the big wire to the battery. Been OK since.

This was how I solved my problem I'm sure someone is going to tell me that they have a better/bigger/faster/slower/cheaper/home made solution.

Thanks for the response. I'm not finding much info on fitting a self-exciting regulator to an alternator.

Go to an alternator rebuilder, good opportunity to have your alt checked out. Yellow Pages

The trip to the alternator shop cost me $38 to get it converted and cleaned up.

I still recommend the pigtail from Painless. The wire with the bulb pictured is the blue one in the 2-pin plug by the firewall. Easy.

http://www.painlessperformance.com/Manuals/30707.pdf

Rich

Rich-
I can't seem to find the blue wire in the two pin plug by fire wall. On my 87 n/a the only blue wire I see is grouped with 6 other wires and goes to a big round 7 pin connector. (Drivers side)
Am I missing something? There is a black and brown that goes to a two pin . . .
Thanks-