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1 wire or 3 wire alternator???

48K views 34 replies 17 participants last post by  70Caprician 
#1 ·
Our sbc engine has a 3 wire alternator on it, but I'm replacing it when we wire up the car, so we can go 1 or 3. What's the difference? Is one better than the other?
 
#4 ·
Doc here, :pimp:

If your of limited Electrical experience, and just want to "Git Er Dun" .. Or space issues..

Then, A one wire is the best way to go..Although it has it's drawbacks..No Direct provision for Lamp or Amp gauge connections..(unless inductively coupled), But you only have One wire and ground to deal with, and you Can ALWAYS use a Voltmeter.

If you go 3 wire internally regulated, you can direct couple an Idiot lamp and AMP gauge..to integrate it into a stock harness & instrument cluster..It takes a bit more expertise & Time, but nothing earth shattering if you can follow a schematic..and have some basic tools..

A 3 wire External, takes a lot more expertise, because you need to throw a regulator into the mix..and make it all play, but again, If you have some knowledge, you should be able to do it..

They all will perform as advertised, and last about the same, So it really boils down to your personal preference, skill & Tool level possessed.

Doc :pimp:
 
#6 ·
OK, on a regular 3 wire late 12SI GM alternator, there is one large wire from the battery to a lug on the rear of the alternator. There are two other terminals on the alternator side, one marked 1 the other marked 2. The terminal 1 isd to be used for a charge light, connected to the charge light circuit. Alternators that are in circuits that have wither a voltmeter or ammeter don't need this charge light circuit to function.

Now, for terminal 2. This terminal is a power source for the internal regulator. In a 3 wire wireup, the number 2 terminal is literally connected to the larfe lug on the rear of the alternator, from the battery. The large wire to the rear lug, and a jumper fdrom there to the number 2 terminal will make the 12SI internally regulated alternators function.

That said, 1 wire 12SI alternators are simply the exact same alternator as a 3 wire, but they use a specially excited regulator designed for industrial, farm and fleet useage. These special regulatos have the large lug to terminal 2 jumper connection INSIDE the alternator. This is the ONLY difference between the 12SI 1 and 3 wire alternators. The number 2 term is connected to the BATT lug either inside or outside the alternator, NOTHING else is different.

12SI alternators are available in 65, 78 and 94 ampere versions.

There is a CS alternator that uses the same type of internally excited alternator, in the smaller overall size. My 1986 GMC Safari van has the 105 amp version.

Early 10SI remote regulator alternators can greatly benefit from using a Wells VR715 regulator. These regulators are electronigc and perform as the later internally regulated 12SI regulators do. Using the Wells regulator will also stop the light fluctuations at idle speeds, lights going from bright to dim to bright to dim. The stock regulators are servo actuated, in essence, they turn the alternator stator on and ott and on and off to regulate voltage production. What is seen in the fluctuating lights is the servos turning the alternator stator on and off and on and off, constantly. The Wells style electronic regulator simply turns the stator on and keeps it on, and when charge volt level reaches a set point of 14.60, the regulator drops excess charge voltage pas the cut off point, to ground, thereby keeping the charge rate and voltage constant, and the alternator gets much less of a workout to do its work.

The stock Delco regulator cap will fit the Wells, making for a stock appearance for restorers.
 
#7 ·
Thats how I wired my jeepster. I got rid of the original problematic alt and regulator and installed a GM 3 wire, then I used a jumper to jump the large terminal (bat) to the #2 terminal. I dont use a gauge or idiot light so I dont need the 3rd wire. I got the rebuilt alt from the parts store for 39.95 and now I have a one wire alt fairly cheap.
 
#10 ·
Sorry did´nt mean to get at you personally, but if the search feature was used more folks could arm themselves with more info before they posted.
There are several threads covering this very topic, and even though I considered the post "Done to death" I did offer a site comparing 1 and 3 wire alternators.
I see you were online when I began this reply, so don´t go, stay and share your knowledge.
 
#12 ·
1 wire or 3 wire

Thanks again guys, and for the record; I searched the posts and read over 20
That came up, but didn't quite get what I needed. The link to mad electrical however was just what I was looking for. The beauty of this site is, you get to wade through tons of opinions and points of view and learn enough to make your own informed decisions.
Thanks again.
 
#15 ·
1 wire or 3 wire

Doc. Decided to go 3 wire. We are putting A/C in it, plus a whopping sound system (this is for my 16 year old son), and I have experience with older cars, domestic and foreign, that dim the lights when you let off the gas, so it just seemed like the 3 wire was the ultimate system, and worth my effort to figure out how to wire it. Even if the difference isn't that drastic, I can't believe the "wiring" will be that drastic either.
Thanks again to everyone that contributed to the lesson.
 
#17 ·
oldguy829 said:
Doc. Decided to go 3 wire. We are putting A/C in it, plus a whopping sound system (this is for my 16 year old son), and I have experience with older cars, domestic and foreign, that dim the lights when you let off the gas, so it just seemed like the 3 wire was the ultimate system, and worth my effort to figure out how to wire it. Even if the difference isn't that drastic, I can't believe the "wiring" will be that drastic either.
Thanks again to everyone that contributed to the lesson.

Doc here, :pimp:

KEWL! It's not THAT hard to wire either..

I always approach my descriptives from the point of view that the reader has never SEEN a wire before, that way the most basic information is put out..and the person doesn't get insulted..

However, If you have had any wire experience at all, It'll be a piece of Cake!

Thanks for the reply Back! :thumbup:

Doc :pimp:
 
#18 ·
I'm curious about why the lights dim on older cars when you run a 1-wire alternator. I think I have heard the the alternator does not "kick in" until the engine speed hits a certain point, but after that isn't the output determined by the system voltage? Why would an older car get dim lights at low engine speeds if the regulator is working correctly?

Man I wish I had seen this thread before I rewired my V8-Sonoma!! I just got a '71 Nova project, and would like to simplify the wiring when I re-do it.

Docvet, I think you're right down the street from me. I live in WC! :thumbup:

Dave
 
#19 ·
bluesman123 said:
I'm curious about why the lights dim on older cars when you run a 1-wire alternator. I think I have heard the the alternator does not "kick in" until the engine speed hits a certain point, but after that isn't the output determined by the system voltage? Why would an older car get dim lights at low engine speeds if the regulator is working correctly?

Man I wish I had seen this thread before I rewired my V8-Sonoma!! I just got a '71 Nova project, and would like to simplify the wiring when I re-do it.

Docvet, I think you're right down the street from me. I live in WC! :thumbup:

Dave
Dave,

Yup, I'm over in Lafayette off Walnut and Mt Diablo (where the old Lafayette Gas used to be) all the way down that road, tucked away up on a private road bordering the mountain and creek..

Self excitation (sensing) is usually the culprit on your question..But I've only seen it a few times when the Alternator was at or below system demands..

Also SOME have nothing to do with the charging system at all, but bad grounds, bad wires, and failing diodes..(not all, but lots of thing can cause this, even a loose belt..)

Doc :pimp:
 
#20 · (Edited)
More info from MAD, http://www.madelectrical.com/electricaltech/howitworks.shtml
he covers the light dimming problem a few paragraphs down.
Check out the last paragraph,"The Best Plan" I did just that as my battery is in the back. Up front on the passenge side is a distribution terminal fed by the alternator, to there other main electrical needs connect plus battery. I also placed one on the firewall drivers side for my MSD and one in front drivers side for the fan relays, headlight relays and my door solenoid relays. Saves on running many wires across the car, just one from terminal to terminal.
 
#21 ·
1 or 3 wire alternator

Great information. How about going a step farther. There are 100 amp, chrome, 3 wire alternators on ebay for around $75.00. they are listed as "GM" not Delco. Is this a desirable piece, or junk? how can I tell?
Fatrodder also lists a 21 circuit (more than I need) wiring harness for around $120.00. Is there a big difference between the quality of this system and a "name" brand? or is the "ease of installation/tech support" the difference?
Will I need to also purchase the terminal blocks/relays/fusible links etc. recommended in the articles no matter which harness I buy?
MADD electrical looks like a quality outfit, but what I saw were components, which would require me to design my own harness and order the parts. Over my head I'm afraid. I feel capable of following instructions and wiring the car, but maybe not up to adding relays and terminals blocks in the right places, or upgrading the wiring size for a backseat battery mount, without some very specific instructions. What would you recommend for the prolific do it yourselfer, with limited electrcial expertise.
 
#23 ·
oldguy829 said:
Great information. How about going a step farther. There are 100 amp, chrome, 3 wire alternators on ebay for around $75.00. they are listed as "GM" not Delco.Is this a desirable piece, or junk? how can I tell? .
You can get rebuilds (NOT GM) from the parts store for like $20 to $60 bucks..and not take a chance, will it work, will it arrive? and if not, can just go back and get a replacement..over the counter..


Fatrodder also lists a 21 circuit (more than I need) wiring harness for around $120.00. Is there a big difference between the quality of this system and a "name" brand? or is the "ease of installation/tech support" the difference?

Will I need to also purchase the terminal blocks/relays/fusible links etc. recommended in the articles no matter which harness I buy?
There is a Thread on this forum, titled " Wiring harness, which do you prefer?" Has about 300 replays on it, about the pros and cons of different harness kits..I suggest you go there and read the information first hand from those that have used them..Ron Francis (owner of Ron Francis harness's ) and the owner of EZ 2 install are both on that thread too answering any TECH questions you may have..

I feel capable of following instructions and wiring the car, but maybe not up to adding relays and terminals blocks in the right places, or upgrading the wiring size for a backseat battery mount, without some very specific instructions. What would you recommend for the prolific do it yourselfer, with limited electrcial expertise.
Most of those harness come with very easy to use Instruction manuals, some more involved than others (this is where that other thread will be helpful in deciding) Actually if you have rudimentary Wire skills, you SHOULD be able to do the job no problem! (Solder, strip, read and follow a schematic, wire color coding , wire gauging) I always suggest go to the car with the instructions and read, and read until you can do it in your sleep before you start..know where everything is supposed to be..and if you get stuck..were all here to help if we can!

Doc :pimp:
 
#25 ·
Doc here, :pimp:

If you go with the 3 Wire (more preferred) Here is a diagram for that, you say it's 3 wire now, but as I understand it you will be going to a new engine harness, with options..

This is 3 wire internal:



Simple and easy to hook up, Run one 10 gauge red wire from the main (large lug) Bolt on the Alternator to the area of the starter solenoid battery main bolt.

On that wire, Install a properly gauged fuse link . If your new Alternator is 80 amps go 85 or 90 on the link.Hook it to the main battery terminal on the starter solenoid.

The second wire, will be a red 12 to 14 gauge wire to any voltage source, switched (I find is better) but "Hot at all times" is how the factory did it..Either way is fine!

Next run an 18 Gauge Brown/White wire from the #2 terminal, to the "Hot in Run" Side of the ignition.

If you have a Charge light, Run an 18 Gauge Brown to one side of the indicator, Exit that with a Pink 18 gauge wire into a fuse/Fuse holder, into a pink/black 18 gauge wire to the "Hot in Run" side of the ignition.

Unless you have an 81 Alternator, disregard the 3 rd red wire, not used.

INSTALLING CONNECTORS THAT WILL LAST:

Do NOT just use Crimp on Connectors, Use a proper size uninsulated ring and, IF needed , uninsulated, Solder-able Butt splices.

To do the job right, Strip the wire to the proper length, about 1/8 on an inch extending out the terminal, no bare wire to the rear. Tin the wire with 50/50 solder. Then slide 2 each, about 2 inch heat shrink tubing over the wire and go to the terminal.

Next tin the Terminal wire "Barrel" (where the wire goes through) until good and smooth and shiny. Then slide your wire into the ring, make sure you have no uninsulated wire hanging out the back.. AND no wire into the ring hole, trim if needed!
Crimp it firmly. Next, solder it, adding a small amount of solder as you heat it, until you get a smooth shiny connection..

(Grayish or dull is a cold joint, reheat, and add a tiny bit of solder until you get the above results.)

Let it cool, then slide the first piece of shrink tubing over the ring and wire, hold or prop the wire STRAIGHT and shrink with a heat gun.

(If you have like for days..a hot hair dryer will work, but take tons of time..Don't use a lighter, or solder gun..this just melts the tubing and possibly the wire below it.)

Next, slide the second piece of tubing over the first, but offset it by about a 1/4 of an inch, holding it straight out (if it won't stand straight on it's own by now ) Shrink it down also. Let it all Cool down, and move on!

This will not only provide insulation at the terminal, but some amount of wire strain relief, and It looks REAL pro done if you do it right. BE SURE to make your tubing end cuts straight..(HINT: use a paper cutter, with an adjustable fence.)

On the Butt Splices (If you must use them) Use a proper gauged splice, Metallic, (no insulation) Look at the splice, you will note an inspection hole that goes to both sides of the splice..

Strip, prep, and tin your wire as you would for ring terminals.

Slide your wire into the splice end (trim if needed so some insulation fits in there) Crimp the one side. Do the same on the other, but before you commit yourself, slide two lengths of shrink tubing over the wire, the first to be about 1/8 inch longer than the whole splice, the next slightly longer, about a 1/2 inch..

Crimp, then find the inspection hole, using a vise or something to hold the wire, Heat the Metal Splice and feed a small amount of solder in the inspection hole..continue to do so until it has filled it in.

Then Slide the LONGER shrink tubing over it and shrink it down, Next slide the shorter one over that and shrink down. This will give you good insulation, and anti chafe, Plus with the inset ends looks again real pro done!

Use this method For all smaller gauge wires (10 Gauge and down) and you will have a system that will last forever, and look good while doing it!

Larger gauge wires (Battery Cable, Frame to body cables, ground cables) Require a Nicopress to install the crimp ends..Don't solder them It will just heat and drip out the ends..Don't try crushing them in a vise..usually the first time it is stressed the wire will just pull out..

If you don't have one ( and I suspect you don't) Have the hardware store, Electric supply, or an electrician install them, they will have the tool.

Everything you never wanted to know about harness Building 101..

Hope it helps, gives you some direction, and hopefully apply it to your new harness install as well..

Doc :pimp:
 
#26 ·
i'm sure soldering is better, but if you have a racheting crimping tool, (and maybe even if you don't, as long as you do a pull test) you have nothing to worry about with crimp-on connectors. ignition man, you aint goin nowhere....
somebody ought to mention using a resistor wire or a radio shack 10 watt 10 ohm resistor or you'll do like me and blow every light bulb in your car (or truck in my case)
 
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