Alternator Upgrade Wiring

[TheSeeker]

Hello, I am currently installing my new 12 SI alternator to my replace my stock one. I am following the directions in this thread - http://67-72chevytrucks.com/vboard/s...d.php?t=119379

It is going failry well, however he states that there is only 3 wires running to the alternator in his harness, white red and blue. I have 4. White, red, blue, and black. I am assuming that the black is a ground? Is this ok to hook up to the alternator case as the stock one was? Or should this black wire not be there.. Thanks!

Engine: 250 IL6
Alt part # http://www.summitracing.com/parts/TFF-7127NI

[VetteVet]

There are a few ways to do this and they are all fairly simple. to answer your questions.
1. There is a ground wire in the stock harness that runs from the alternator to the external voltage regulator.
2. The 12 SI alternators and the 10 SI for that matter are internally grounded so they do not require a separate ground as long as the alternator mount is grounded to the negative battery cable. Do a continuity check on your black wire and you'll find that the black wire does go to the ground at the regulator.

Here's a picture of the alternator with the ground wire attached.



If you decide to keep the external regulator harness, You will need to disconnect the regulator plug and jump across 4 wires.
The brown wire from the firewall on the no 4 terminal on the regulator will jump to the white wire on terminal 2.

The red wire on terminal 3 will jump to the blue wire on terminal 1

Here is the stock wiring.




Here is the jumpered diagram for the conversion.




Here is how the 12 SI is wired



It's easy to get confused because some guys will get the blue and white wires crossed from the regulator to the alternator. Just remember that the brown wire goes to the no. 1 wire on the SI alternator and the red wire from the regulator goes to the no. 2 terminal on the alternator.

In your link by TODDtheODD He uses the blue wire instead of the white one to extend the brown wire over to the no.1 terminal on the alternator.
Then he just loops the no.2 terminal over to the large post on the alternator.
This is an easy way to get power to the no.2 terminal on the alternator but,
In my opinion it is not as good a way to do it as running the red wire from the
external regulator plug via the blue wire to the no.2 terminal on the alternator.

The reason for that is because while the loop will work OK it is not as efficient as extending the red wire from the regulator plug because of a term called
" voltage drop ". The no 2 terminal on the alternator is the sensing terminal for the alternator regulator. It tells the regulator what the voltage is in the charging circuit and the regulator allows more or less amperage into the alternator fields to vary the output of the alternator.

Due to voltage drop the voltage is going to be less the farther away from the alternator you get so you want the alternator to compensate for that and give more voltage to the loads in the circuit down stream from the alternator.


Now if you want to clean up the harness and get rid of some wires you can do it like I do in the diagram below. The wiring is essentially the same if you trace it down, The brown wire goes to no.1 on the alternator and the red wire which is always hot goes to the no.2 on the alternator.

[ray_mcavoy]

The alternator is usually grounded to the engine through it's mounting brackets. But some years did include a black ground wire in the harness.

I'd also recommend running the voltage sensing wire back to the factory power distribution point (instead of a short jumper wire to the alternator BAT stud). That'll take advantage of the alternator's ability to boost the voltage as necessary to compensate for any voltage drop in the wiring. See the posts by VetteVet in this thread --> http://67-72chevytrucks.com/vboard/s...74#post6552374 EDIT: no need to reference that other post ... looks like VetteVet just gave you that info while I was busy searching for that other thread

[TheSeeker]

Wow!! Thanks guys, perfectly simple so even a dunder head like me gets it. So in short, cut the wires from the regulator plug, and throw that out.. Then red to blue and brown to white.. Then plug red to alt power, and the brown to plug 1 and blue to plug 2 on the alt? That sounds so simple it must be too good to be true haha

[ray_mcavoy]

Originally Posted by TheSeeker

... So in short, cut the wires from the regulator plug, and throw that out.. Then red to blue and brown to white.. Then plug red to alt power, and the brown to plug 1 and blue to plug 2 on the alt?

Yes, that's about it. Although with the brown wire spliced to the white wire (at the old regulator location) you'll have a white (instead of brown) color code on the end going to the alternator's #1 terminal.

Or if you're like me and don't like to cut the plugs off the wiring, you can get an adapter kit that basically does the same thing in a plug-n-play manner --> http://www.summitracing.com/parts/aww-27555/overview/

[bmw-Hauler]

Great instructions and Pic's

Thanks Barry

[1968aj]

thought this might be the place to ask. my 71 has a 2005 5.3 conversion. there is a wad of wires all taped together that used to go to the voltage regulator.they are not plugged in and seem to go no where.what should I do with them? do any of them need to be connected? trying to solve a low voltage problem. all the wires for the 5.3 are now wired straight to battery. any ideas? THANKS

[VetteVet]

What you have there is a CS style alternator, probably a 130 or a 144. The wires that are taped up are most likely the old external voltage regulator from the stock harness. Look for a brown, red, blue, and white wire.

What you do next depends on how the alternator is wired. Is it a conversion by the previous owner or is it part of the stand alone harness for your 5.3? Look at the plug for the alternator and see how many wires are plugged into it. The earlier ones had four wires and the 94 and later had one wire, a small brown wire. If it has four wires then most likely it is controlled by the PCM, but if it is a two wire plug it has been converted by someone. If it only has the one brown wire then it could be either one and you'd have to trace the brown wire to know for sure.

Saying you have a low voltage problem isn't telling us much. Measure the alternator output and give us the reading. 12 volts is battery voltage and the alternator isn't charging. 13 volts means the alternator is charging but not enough. Running all the wires to the battery is not the best idea. You need to run the alternator and the battery to a main junction or a fuse panel and feed everything from there.

[Andy4639]

Just to throw my 2 cents in.

If your doing away with the external V-R then take the wiring from it and unravel it out of the harness and just run the wires straight to the alternator. Then you don't need any jumpers are connectors except for what you use at the alternator on the ends.
Makes for a lot nicer looking install and you don't have wires all taped up inside the harness.

[VetteVet]

Originally Posted by Andy4639

Just to throw my 2 cents in.

If your doing away with the external V-R then take the wiring from it and unravel it out of the harness and just run the wires straight to the alternator. Then you don't need any jumpers are connectors except for what you use at the alternator on the ends.
Makes for a lot nicer looking install and you don't have wires all taped up inside the harness.

Post up that picture of your engine Andy.

[Andy4639]

This is in my 64 SS Impala upgrade. All the info is the same.

I just swapped this on the 64 SS Impala. 85 buick Revieria 94 amps. Its pretty easy to.
This was done using a 71 Chevy C10 alternator bracket on the SS also.

Run the brown wire on the external Chevy regulator plug over to the alternator no. 1 post.

Run the red wire on the Chevy external regulator plug to the alternator no. 2 post.

Connect the red alternator output post to the back of the new alternator.

Your done.

Now hook up your voltage gauge.
Info is from VetteV not me. He has helped me more than I can ever hope to help him.

[1968aj]

I have a little more than 14 going to alternator. voltage gauge on Dakota gauges shows 11. when I turn on headlights and wipers it drops to 10. the wad of wires that went to voltage regulator and the old alternator wires are not attached to anything.wire to new alternator are direct from battery.

[saxart]

I went through this same thing with my '70 this past winter. Here's a link if if helps. Many of the same helpful folks that are helping you helped me.

http://67-72chevytrucks.com/vboard/s...d.php?t=757426

[Andy4639]

All the factory gauges work as suppose to even the amp gauge. I installed the volt gauges in both. My Impala runs at 14.35 with brights, radio on until the AC & fans kick on. Then it drops to around 13. This is at idle.

[VetteVet]

If I'm looking at it right he has a CS alternator which is going to need the resistor in the exciter wire. Instead of the no. 1 and no. 2 terminals like the SI alternator, he will have the S and L terminals in the alternator along with an I terminal and a P terminal which are not used. The resistor will go in the wire to the I terminal and the S terminal is the voltage sensing terminal. If it is run directly to the battery positive then his regulator in the alternator will sense that the battery voltage is 12.6 volts and will not compensate for the voltage drops at the headlights and the starter and HEI distributor.

The readings he is getting would confirm this. That is why it is best to have a main junction to connect everything to including the sensor wire. This would allow the alternator to read the downstream voltage drops and charge more to compensate for them.

I suspect that we will have to sort this out in a few more posts and with information provided by the OP. Not to worry we have done it many times before.