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I'm a mechanical engineer so most of this electrical/electronics are over my head. What is the cleanest, path of least resistance to getting the alternator up and running on a swap? My harness, PCM, etc. are from a 2005 Suburban with the L59. The connector for the alternator is a 2-pin with gray and brown wires. I did not take the alternator from this truck while I was at the junkyard. I can pick up a 4-wire, 4-wire connector with the only two wires, or 2-wire. I also don't mind swapping the wires/pins to different outputs on the PCM. I rebuilt the wiring harness with the info from the LT1Swap website. He suggests putting the brown wire into socket 15 and the grey wire into 74 of the green connector to "MODELS WITH GENERATOR BATTERY CONTROL MODULE, REWIRE ALTERNATOR BROWN WIRE TO THIS PIN TO REMOVE GBCM".
I'm a mechanical engineer so most of this electrical/electronics are over my head. What is the cleanest, path of least resistance to getting the alternator up and running on a swap? My harness, PCM, etc. are from a 2005 Suburban with the L59. The connector for the alternator is a 2-pin with gray and brown wires. I did not take the alternator from this truck while I was at the junkyard. I can pick up a 4-wire, 4-wire connector with the only two wires, or 2-wire. I also don't mind swapping the wires/pins to different outputs on the PCM. I rebuilt the wiring harness with the info from the LT1Swap website. He suggests putting the brown wire into socket 15 and the grey wire into 74 of the green connector to "MODELS WITH GENERATOR BATTERY CONTROL MODULE, REWIRE ALTERNATOR BROWN WIRE TO THIS PIN TO REMOVE GBCM".
If you have a PCM already, then you can wire it directly. What is being done here is allowing non-stock controlled motors to use the newer 2-wire alternator.
Ok. I thought in the original post he was saying you need a 2006+ ECM and BCM to make it work. Which made me think the ECM alone wouldn't make it work.
I'm a mechanical engineer so most of this electrical/electronics are over my head. What is the cleanest, path of least resistance to getting the alternator up and running on a swap? My harness, PCM, etc. are from a 2005 Suburban with the L59. The connector for the alternator is a 2-pin with gray and brown wires. I did not take the alternator from this truck while I was at the junkyard.
If your harness, PCM combo already have the two pin connector, then chances are you don't need to bypass anything with an external PWM generator. In that case, just pick up an 2 pin alternator and you should be good to go.
This thread is for people who have the 2 pin alternator but have an older PCM that doesn't support the 2 pin alternator.
If you have a 4 pin or other alternator, then this thread doesn't pertain unless you want to buy a 2 pin regulator and swap that into your alternator.
I’ve purchased both controls in this thread. The first control from page 1 requires a 5v input source, which I had a hard time finding and gave up on it because I didn’t want to hack into my harness to steal from a reference wire. The second unit that Bill Birmingham talks about allows you to use a 12v input source, and adjust the control to a 5v output, which the alternator wants. It works wonderfully. I also had Bill build me an enclosure for it that he talks about and shows a picture of in this thread. All in all, I could be happier. For around $30 bucks, including the enclosure, I can get anything I want from my alternator due to the adjustable control.
The module that Tick offers appears to do the same thing, without adjustments, for $100 more. No thanks.
The original thread is about reusing a 2-pin alternator. I came to it for help about how to make my standalone swap work in a 1986 CUCV. I made it work with my homemade standalone harness. I'm reporting back my results. I don't care if it helps you specifically. But hopefully someone will find it useful.
The original thread is about reusing a 2-pin alternator. I came to it for help about how to make my standalone swap work in a 1986 CUCV. I made it work with my homemade standalone harness. I'm reporting back my results. I don't care if it helps you specifically. But hopefully someone will find it useful.
Ok, well hopefully since you're a NASA engineer you've also checked to make sure that you're not getting limp mode voltage/amperage, and getting full output. Because, you're right at limp mode voltage. Would suck to give a tutorial on how to do something, and be totally wrong. Toss a 100A load on it and see if it remains at 13.75.
Ok, well hopefully since you're a NASA engineer you've also checked to make sure that you're not getting limp mode voltage/amperage, and getting full output. Because, you're right at limp mode voltage. Would suck to give a tutorial on how to do something, and be totally wrong. Toss a 100A load on it and see if it remains at 13.75.
Mechanical engineer and fully ignorant of electrical stuff. Hence why I am here asking for help. I can, however read and follow instructions. If you know I am doing something wrong than please point me in the right direction.
Mechanical engineer and fully ignorant of electrical stuff. Hence why I am here asking for help. I can, however read and follow instructions. If you know I am doing something wrong than please point me in the right direction.
13.75 is the limp mode voltage. If you give the alternator no inputs or the wrong inputs, it defaults to 13.75. Around 14.1 is a common charging voltage when the alternator is driven correctly.
Please point us to the directions you followed. I'm curious.
13.75 is the limp mode voltage. If you give the alternator no inputs or the wrong inputs, it defaults to 13.75. Around 14.1 is a common charging voltage when the alternator is driven correctly.
Please point us to the directions you followed. I'm curious.
Thanks for the info. I could not find specific directions for my scenario. I rebuilt an 03 LM7 with the harness and alternator from an 05 L59. I used the info at https://lt1swap.com/2004vortec_pcm.htm to rebuild the harness. He indicates you move the pins to these locations to delete the GBCM. I guess I assumed I could get away with deleting it and avoiding putting an inline resistor like I have seen around this website. Most swap info I have found on here is for 2-wire. I'm in the process of installing a painless chassis harness. If I cannot make a working alternator with just the engine harness it would be a good time to wire it into the chassis.
Maybe a dumb question, but why is 13.75 volts not sufficient? The one-wire alternators were set to 13.4 volts I thought.
My truck is a 1986 Army truck. It has the normal lights required to pass inspection, mechanical fan, no radio, and heat only. I can't imagine I will be taxing the electrical system...
Maybe a dumb question, but why is 13.75 volts not sufficient? The one-wire alternators were set to 13.4 volts I thought.
My truck is a 1986 Army truck. It has the normal lights required to pass inspection, mechanical fan, no radio, and heat only. I can't imagine I will be taxing the electrical system...
13.7 volts can operate a car well enough, no matter how much or how little load there is. It's just not high enough to properly charge the battery to it's full potential. https://www.popularmechanics.com/car.../a108/1272526/
hi i have a 2 wire alt but im running a carb on my motor i just want to wire the alt ive read a few forums some people say 13.5 volts is good i just hook it to the battery im not a wiring guro but i just want to get the car running its my first ls motor and i feel like going back to my big blocks i have a 80 chevy malibu ill be running two fuel pumps one for the motor and one the nos also eletric fans no big radio just two little speakers also a turbo 400 with a trans brake any help thx
05-29-2020, 12:40 PM
