A little alternator schooling needed

[Mrturner1]

Long story short, bought an alternator from a guy and after testing, it's half the amperage he said it was. Looking at getting it re-spun to 120 amp or replacing with a Powermaster 150.

Here's where I need some info from you guys so I can be fluent in alternators and their wiring. My current setup is the rectangular plug with two wires in it, and also has the 12v going to the threaded stud on the back. This is a 2 wire correct? Also, what would it take to switch to a 1 wire and would it benefit my rig at all to do so?

[ray_mcavoy]

The old externally regulated alternators had a square shaped 2-wire plug connecting them to the regulator. With more of a rectangular shaped 2-wire plug, you probably have a 10SI or 12SI internally regulated alternator. See here for more info on these --> http://www.madelectrical.com/electri...elcoremy.shtml

I'd recommend staying with the stock 3-wire setup. The 1-wire alternators can be easier to hook up but lack remote voltage sensing which is a bit of a downgrade. See here for details --> http://www.madelectrical.com/electri...hreewire.shtml

Also, when getting into 100+ amp territory, I'd recommend going with one of the newer CS-series alternators.

[Chknlyps2]

Lots of good info in this thread http://67-72chevytrucks.com/vboard/s...d.php?t=692750

[RichardJ]

What you have is a 3 wire installation that is wired incorrectly. More than half the guys on this forum have theirs wired the same and will argue until they are blue that their alternator is wired correctly and that it works perfectly.
Close but no cigar.

Mad Electrical offers a good explanation, but is spread out over three long pages.

http://www.madelectrical.com/electri...hreewire.shtml

50 guys are now ready to jump in and tell you I don't know what I am talking about. I'll stay with the way GM wired these SI alternators.

[Mrturner1]

Originally Posted by RichardJ

What you have is a 3 wire installation that is wired incorrectly. More than half the guys on this forum have theirs wired the same and will argue until they are blue that their alternator is wired correctly and that it works perfectly.
Close but no cigar.

Mad Electrical offers a good explanation, but is spread out over three long pages.

http://www.madelectrical.com/electri...hreewire.shtml

50 guys are now ready to jump in and tell you I don't know what I am talking about. I'll stay with the way GM wired these SI alternators.

How does GM wire them?

[Andy4639]

I like the GM way better than the 1 wire! GM did it right. Only thing I would do is loose the external voltage regulator.
No there is no benefit over a 1 wire other than it being less wires to hook up.

[Mrturner1]

How did GM do it?

[davepl]

This is how I do mine. I presume it's the same as GM, but this is a little diagram I made or found long ago that I use as a reference when converting to internal regulator. Ignore the part at the External regulator where I'm looping things around, just presume they're connected to the regulator like always (unless you're converting to an internal regulator, then this shows how to cut and loop them).

This is for my Pontiac 2+2, and our trucks may not use a horn relay in the same way, so the big red wire can just go to the battery or the major junction lug near it.

I would presume with a one-wire or incorrectly wired 3-wire that you lose your ammeter gauge as there's no sense/reference line for the gauge to compare against.

[cooperhw]

Originally Posted by RichardJ

What you have is a 3 wire installation that is wired incorrectly. More than half the guys on this forum have theirs wired the same and will argue until they are blue that their alternator is wired correctly and that it works perfectly.
Close but no cigar.

Mad Electrical offers a good explanation, but is spread out over three long pages.

http://www.madelectrical.com/electri...hreewire.shtml

50 guys are now ready to jump in and tell you I don't know what I am talking about. I'll stay with the way GM wired these SI alternators.

I agree with this^^^ madelectrical.com kinda spells it out plain and simple. I am currently installing my second wiring kit (underhood) because the first one on Homer was a "Home Run" in my opinion. Call Mark at Mad Enterprises 559-539-7128 if you have any questions. He is REALLY smart on this subject (but he does love to talk). I've talked to him a couple times and he knows this subject matter inside and out.

[slikside]

Yeah, don't go the 1 wire route. Easier, yes...that's why some have done it. But definitely not better.

As was said, you lose remote sencing of voltage, and you really want that. It ensures you have proper voltage (13+?) all the way back at the battery so the battery gets fully charged. Otherwise, all the system is doing is reading alternator output right at the alternator, and regulating based on that. So by the time you account for the voltage drop over the length of your wire to the battery, you aren't getting what you should to fully charge the battery.

Now that I think about it, I might be describing how some have "looped" a couple terminals on the back of the alternator, but I believe much the same happens on the 1 wire setup.

BTW, VetteVet is "The Man" for all things electrical on this site...if you see his advice here, follow it.

[davepl]

One thing I've always wondered about the three-wire with voltage sense: let's say you have a big voltage drop in your circuit such that there's a 4 volt drop. To get 12V at the sense line the alternator has to kick out 16V, which is fine in that it'll be down to 12V by the time it gets to the dash... but doesn't that cook the battery then?

My point is that everything doesn't have the same resistance or run length, so bringing up the voltage to compensate for the drop to the sense line would seem to oversupply things closer (in resistance terms) to the alternator.

[swamp rat]

Originally Posted by Mrturner1

How did GM do it?

3 wire.. On internally regulated systems.

[ray_mcavoy]

Originally Posted by davepl

One thing I've always wondered about the three-wire with voltage sense: let's say you have a big voltage drop in your circuit such that there's a 4 volt drop. To get 12V at the sense line the alternator has to kick out 16V, which is fine in that it'll be down to 12V by the time it gets to the dash... but doesn't that cook the battery then?

My point is that everything doesn't have the same resistance or run length, so bringing up the voltage to compensate for the drop to the sense line would seem to oversupply things closer (in resistance terms) to the alternator.

In the stock configuration for 67-72 trucks, the remote voltage sensing wire is connected to a "main junction" splice located in the harness on the driver side of the firewall. So the system is regulating the voltage at that main junction. Both the battery charge wire and the main feed wire into the cab are connected to the main junction and therefore see the regulated voltage.

However, if a person were to connect their own battery charging wire directly to the output of the alternator (which as you pointed out can be at a higher voltage), that could result in the battery being over charged.

[VetteVet]

Originally Posted by ray_mcavoy

In the stock configuration for 67-72 trucks, the remote voltage sensing wire is connected to a "main junction" splice located in the harness on the driver side of the firewall. So the system is regulating the voltage at that main junction. Both the battery charge wire and the main feed wire into the cab are connected to the main junction and therefore see the regulated voltage.

However, if a person were to connect their own battery charging wire directly to the output of the alternator (which as you pointed out can be at a higher voltage), that could result in the battery being over charged.

Quoting Ray to show you guys how simple this conversion is.

This is the junction he is talking about on the left side of the truck taped up in the harness. This is mine which has the charging light and not the battery gauge, so the black ammeter wire with the white stripe is missing.


The four red wires soldered together is the junction. You can also separate them and use an aftermarket junction if you desire.





Now here is how easy it is to convert to the 10 or 12 SI alternator. Use a 12 if you can find one.

You need to get a different plug for the SI and any parts store carries them
They usually come with a red wire and a white wire already installed. check the wire colors with the plug inserted and most of the time the white wire will go to terminal no.1 on the alternator body and the red wire will go to terminal 2.

Now here's the easy part.

Pull the external regulator plug and locate the brown wire 16 gauge and the red wire 12 gauge. These are located on terminals four and three on the plug.
Remove them from the plug.

Next connect the 16 gauge brown wire to the alternator plug wire that goes to terminal 1. Probably the white one.
Then connect the red wire to alternator plug wire that goes to terminal 2. Usually the red one.

connect the large red wire that was on the back of the OEM alternator to the large stud on the 12 SI alternator and you're wiring is done.

The mounting of the alternator is the same so I ignored that part.

Now you have two useless wires on the EVR plug white and blue and the old regulator and plug that you no longer need, so you can remove them from the harness for a cleaner look.


The brown 16 gauge wire runs from the firewall block to the external regulator and the red wire from the regulator is the voltage sensing wire from the external regulator to the soldered junction in the harness. This is how clean it looks when you're done.

This is the OEM with the external regulator.




Now here is the clean way to do it. You can also run a larger charging wire from the back of the alternator to the junction If you are using cooling fans or other larger current draws.

[Mrturner1]

VetteVet, the lower picture is a lot like what I have now, except there is no junction block like the one in the top of the picture, and on mine there is no larger 12r power going to the fuse box. Isn't that the one that brings power the the fuse panel? There's a smaller 16 gauge wire that comes from the rectangular plug in the alternator and goes to the fuse panel in the cab, but not a larger one.

The black 18b wire isn't there on mine either

[swamp rat]

To get back on track here Turner you have a 3 wire alternator already, you could have posted a pic of it for clarification. Not saying your alternator is fine by any means.

You know that short red wire looped on the back of your alternator? that is the sensing lead, it should be disconnected from the battery post on the back of the alternator, then a new wire made and routed to the driver side junction block and soldered in. Not having that sensor wire go to the junction block can give the alternator readings that do not account for volt drop, fire the truck up and read voltage on the back of the alternator and compare with readings from the battery and junction block.

With the exception of the sensing lead the wiring is probably fine, I agree with staying away from the one wire alternators, plenty of educational material on why has been posted, less does not always equal more. Just move the lead and buy a different 3 wire alt with the correct orientation of mounts to plug location and your set.

[Mrturner1]

The only thing going from the alternator to the cab, is one 16 gauge wire that is one of the two wires in the rectangular plug into the alternator. The power going to the battery and the sensing wire is one thing, but it seems the bigger problem would be that there's only one wire going to the cab, and it's a 16 gauge. That's a very small wire, and from the looks of the diagram it isn't even the one carrying power, so what is? The truck started and ran so it's gotta be getting power, I just don't know where.

[VetteVet]

Originally Posted by Mrturner1

VetteVet, the lower picture is a lot like what I have now, except there is no junction block like the one in the top of the picture, and on mine there is no larger 12r power going to the fuse box. Isn't that the one that brings power the the fuse panel? There's a smaller 16 gauge wire that comes from the rectangular plug in the alternator and goes to the fuse panel in the cab, but not a larger one.

The black 18b wire isn't there on mine either

Well after searching I saw the alternator in your truck and it's a 10 SI and it has two wires coming out of the plug. The white wire goes through the firewall block and up to the ignition switch. It becomes a resistance wire when it gets inside the cab. The resistance value should be 10 ohms. This is all depending on what the previous owner has done to the wiring. It appears that he has done a considerable amount from your description.

The red wire in your picture just loops over to the main charging wire from the no. 2 terminal on the alternator for sensing purposes. As you have been told this is not the best way.

If you do not have the junction on the right fender with the 18b wire and the fusible link show in my diagram, then the PO has rewired the harness and you will have to determine where the smaller positive wire goes from the Positive battery terminal because that is the one that feeds the cab and fuse panel along with the large red wire from the back of the alternator.

The alternate route is to run the alternator charging wire to the starter solenoid, where the alternator charging wire can charge the battery back through the starter cable, and a smaller wire will run from the starter solenoid to the internal cab, to the fuse panel. Ideally the two wires should run to a main junction on the left fender and from there you feed everything on the truck. This is how GM did it in the post 74 trucks.

If you don't have the 18b wire then you probably don't have the 18b/w wire either. This means that your battery gauge doesn't work or your truck has a voltmeter installed and the battery gauge has been eliminated.
There is a lot of speculation going on because of a lack of details.

Take some advice.

Quit pissing around with this 10 SI alternator and get yourself a CS 144. The wiring connections are almost the same but the alternator plug is different and you can buy an adapter plug that will connect the SI plug to the CS alternator.

Here's why.

The 10 SI was only designed for 60 amps, the internal cooling is inadequate for rewiring since the space for airflow is reduced and you're vents are small in the back to start with. A 12 SI would cool better and the CS 144 is better yet.


This is a CS 130 but they are virtually the same.

[Mrturner1]

Originally Posted by VetteVet

Well after searching I saw the alternator in your truck and it's a 10 SI and it has two wires coming out of the plug. The white wire goes through the firewall block and up to the ignition switch. It becomes a resistance wire when it gets inside the cab. The resistance value should be 10 ohms. This is all depending on what the previous owner has done to the wiring. It appears that he has done a considerable amount from your description.

The red wire in your picture just loops over to the main charging wire from the no. 2 terminal on the alternator for sensing purposes. As you have been told this is not the best way.

If you do not have the junction on the right fender with the 18b wire and the fusible link show in my diagram, then the PO has rewired the harness and you will have to determine where the smaller positive wire goes from the Positive battery terminal because that is the one that feeds the cab and fuse panel along with the large red wire from the back of the alternator.

The alternate route is to run the alternator charging wire to the starter solenoid, where the alternator charging wire can charge the battery back through the starter cable, and a smaller wire will run from the starter solenoid to the internal cab, to the fuse panel. Ideally the two wires should run to a main junction on the left fender and from there you feed everything on the truck. This is how GM did it in the post 74 trucks.

If you don't have the 18b wire then you probably don't have the 18b/w wire either. This means that your battery gauge doesn't work or your truck has a voltmeter installed and the battery gauge has been eliminated.
There is a lot of speculation going on because of a lack of details.

Take some advice.

Quit pissing around with this 10 SI alternator and get yourself a CS 144. The wiring connections are almost the same but the alternator plug is different and you can buy an adapter plug that will connect the SI plug to the CS alternator.

Here's why.

The 10 SI was only designed for 60 amps, the internal cooling is inadequate for rewiring since the space for airflow is reduced and you're vents are small in the back to start with. A 12 SI would cool better and the CS 144 is better yet.


This is a CS 130 but they are virtually the same.

Attachment 1518777


Attachment 1518778

I had the shop go ahead and re-spin that alternator yesterday before reading all this. If the 10si was never meant for anything over 60 amps, it's sure going to run hot now. The guy re-wired it for 110 amps, 75 amps at idle speed...it was only 40 bucks so it's not a huge deal if I have to ditch it.

Sounds like I need to pull everything and re-wire myself (I'm reminded of Davepl's post on not doing it "right" yet lol) so I can rely on it and know everything that's going on in there. Also sounds like a new alternator is in order, checked out a few Powermaster units that looked nice.

[Mrturner1]

The ringlet that goes on the stud on back of the alternator, has a 10 gauge wire but after looking at it it's all frayed and only 2 STRANDS! of wire are left.

[Mrturner1]

Pic

[Mrturner1]

Here's some kind of block or junction

[Mrturner1]

Is that a junction box in the pic above?

[davepl]

BTW, if you're cool like me you make the modification INSIDE the regulator and throw away the guts so it all looks factory.

Which is ingenious until some future owner or tech replaces it with an actual regulator!

[Mrturner1]

Originally Posted by davepl

BTW, if you're cool like me you make the modification INSIDE the regulator and throw away the guts so it all looks factory.

Which is ingenious until some future owner or tech replaces it with an actual regulator!

Very cool I'm looking for a 67 swb and I'm going to do an all factory restoration. I'll be looking for info and tips on that I'm sure.

Looked at some soldering irons today, might try my hand and really do the rest of my wiring the right way