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Old 05-23-2010, 07:15 PM
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3 wire to 1 wire Alt. change

I am changing from a 3 wire GM alternator to a 1 wire. What should I do with the "extra" 2 wires? I've been told to tape them off. Is this good advice?

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Old 05-24-2010, 06:23 AM
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Not really a very good idea, you will have a more reliable charging system with the 3 wire set up . Manufactures are pretty smart about that kind of thing .
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Old 05-24-2010, 06:44 AM
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I try to avoid using the 1 wire alternators, contrary to what the manufacturers say , they do draw the battery down. It's not much, but if you don't start your car or keep it on a trickle charger, the battery will be dead in a matter of weeks. I have had to install a battery cutout switch in several cars to keep this from happening. The extra 2 wires can be taped up, although one is an exciter wire, and if you have a charge light on the dash it will not work right anymore.

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Old 05-24-2010, 08:04 AM
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3 wire - 1 wire comparison.
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Old 05-24-2010, 02:51 PM
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If you already have the wiring in place for a 3 wire, I would not recommend changing to a 1 wire. They don't work as well as a 3 wire and are not real good at all if you have a lot of electrical accessories. A proper setup 3 wire will help to keep your battery healthy for a long time
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Old 05-25-2010, 01:12 PM
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I just went from 1 wire to 3 wire - and all I've ever done so far with my car is run up and down the driveway. The dam' Powermaster alternator wouldn't kick the charge in until I had 'winged' the throttle over 2500 rpm, which is wrong according to the directions, but now charges at idle or thereabouts.

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Old 05-26-2010, 04:08 PM
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I also want to change from a 1-wire to a 3-wire setup.

The alternator is the one supplied with the Street & Performance harness for my '94 LT-1. It's a polished 12SI; I have no idea how many amps it's rated for and I'm having to rely on the assumption that the boys in Mena, AR know what they are doing. Me, sometimes, not so much. The car has power everything, so I'm hoping it's at least the 94-amp version.

I have read the pages at http://www.madelectrical.com/electri...hreewire.shtml and found them enlightening except for one thing: there appear to be both 1-wire and 3-wire versions of the 12SI. How do I know which one I have or can they all be run as 3-wire just by connecting terminal 1 to a switched 12V source (to excite the alternator; an idiot light appears to be optional) and terminal 2 to the fuse panel distribution point (to externally regulate the voltage)?

My fuse panel is a Ron Francis Advantage (great stuff, but not inexpensive) that does have the yellow diode plug "located above terminals #16 & # 17" per the one page of instructions that I found in the car when I purchased it. It alludes to not needing this when using a one-wire alternator (which is how it is wired now) but doesn't say how to wire it for a three-wire alternator (which is what I want). I'm also missing the plastic strips that actually show the numbers of the terminals, so I'm kinda lost as to what terminal is what (and the location of the panel is, of course, awkward so it's hard to read the printing on the wires). I know I can call Ron and ask about this stuff (another car I purchased had an older version of his panel and they were very helpful), but it's after quitting time today and if anybody knows how to wire the panel for a 3-wire alternator, I'd appreciate the info.

And if it's not clear, I'm weighing in on the side of pnt4u keeping his 3-wire system.
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Old 05-26-2010, 04:22 PM
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Quote:
Originally Posted by Irelands child
I just went from 1 wire to 3 wire - and all I've ever done so far with my car is run up and down the driveway. The dam' Powermaster alternator wouldn't kick the charge in until I had 'winged' the throttle over 2500 rpm, which is wrong according to the directions, but now charges at idle or thereabouts.

Dave W
Here's a picture of the back of the alternator.
http://www.madelectrical.com/electri...es/delcor4.jpg

Pull the plug off of the alternator with the engine turned off. Terminal one should read zero volts; terminal 2 should read +12 volts.

Turn the ignition to ON. Both terminals should read +12 volts.

Terminal 1 is supposed to provide +12 volts [only] when the car is running to energize the magnet inside the alternator. If it's not, you get the behavior you describe. If it's +12 volts all the time, your battery will drain when the ignition is off.

I've read that there might need to be some small amount of resistance in the lead to terminal 1 and the idiot light would provide that. But advice varies and it may only be applicable to older GM or maybe non-GM alternators; it's just not clear to me.
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Old 05-27-2010, 10:45 AM
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If I didn't make it clear, you're measuring voltage in the plug, not at the terminals on the alternator itself.
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Old 05-29-2010, 07:32 PM
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Follow-Up

Just to follow up, on the Ron Frances Advantage panel, alternator terminal #1 is wired to panel terminal #16, alternator terminal #2 is wired to panel terminal #2.
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Old 05-31-2010, 03:58 PM
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Quote:
Originally Posted by hduff
If I didn't make it clear, you're measuring voltage in the plug, not at the terminals on the alternator itself.
Thanks for your reply. I finally did get around to check the wiring via recommended procedure and it checked out OK! YIPEEE! No more 1 wire. I now count my alternator with 3 fingers. Not 1. Thank you all for the advice. Once I figure out how to post a picture of my truck, I will do that too.
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Old 03-31-2016, 05:28 PM
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GM Alternator Wiring

Hey Ya'll. I was reading ya'lls posts about this GM 1 wire alternator alternative to the factory 3 wire setup. Read some good advice and wanted to chime in, so I joined. First, I'll say that I am completely ignorant about alternator wiring (as far as what wires are connected where, under the dash) and I will appreciate any and all help from someone who knows. Here's my situation: I just bought a 1985 Chevy S10 Pickup that has a 1980 267 C.I. V8 out of a Monte Carlo (I decoded the engine code). All is fine, except the status of the charging system. The previous owner has wires going here and there, and I have no clue if they are connected to the proper places. Something is wrong because the alternator does not charge properly (if at all). I was considering turning this alternator into a 1-wire set up, by changing the necessary wire connections, thinking this would solve the non-charge issue. But upon further investigation, I believe I want to stay with the recommended original 3-wire set up. So what I have to do is figure out where all these alternator wires are "supposed" to be connected, and I'm betting that I will find that one of these wires is not connected to the proper source. So, attached to the +BATT post (alternator) is one red wire connection that goes through the harness, another (double) red wire connection, going through harness. At the plug connection, there is a brown wire (#1 terminal) going through harness, and a red wire (#2 terminal) that the guy spliced and ran it through the firewall and plugged into fuse box. What I would appreciate is for someone to explain to me where each wire is "supposed" to go, and I believe this will solve the issue (the alternator and battery both tested good at Autozone). Thanks ya'll, and I'm looking forward to hearing from ya's
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Old 03-31-2016, 06:30 PM
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1st you should start your own thread for better responses...

2nd On the alt there are basically 3 connections

The Alt pig tail has terminals 1 and 2

Terminal #1 from the alt goes to the one side of the idiot light on the dash. The other side of the idiot light goes to a switched 12v source (hot when the key is in the run position) This is the exciter wire and tells the alt to start producing juice. The idiot light does not get a ground wire, it gets a ground from the internal regulator in the alt when the alt isn't spinning. That's why it lights when the key is turned to run but the engine isn't running, and it goes out when the engine starts. You do not have to have an idiot light or a resistor, you can have just a switched 12V running to the #1 terminal and it’ll work just fine. (GM it's brown.... ran thru the bulk head connector to the alt charging indicator lamp)

Terminal #2 from the alt goes to the hot side of the wiring system, normally it’s spliced into the hot feed leading to the fuse box. This is the sense wire, it tells the alt to produce more or less juice depending on the demands of your electrical system. (Red to an orange fusible link to the bulk head connector into the back of the fuse panel)

The large lug on the back of the alt is the output wire or charge wire and is normally tied directly to the pos post on the battery via a large gage battery cable.

That's it in a nut shell.
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Old 04-01-2016, 03:39 PM
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Quote:
Originally Posted by EOD Guy View Post
1st you should start your own thread for better responses...

2nd On the alt there are basically 3 connections

The Alt pig tail has terminals 1 and 2

Terminal #1 from the alt goes to the one side of the idiot light on the dash. The other side of the idiot light goes to a switched 12v source (hot when the key is in the run position) This is the exciter wire and tells the alt to start producing juice. The idiot light does not get a ground wire, it gets a ground from the internal regulator in the alt when the alt isn't spinning. That's why it lights when the key is turned to run but the engine isn't running, and it goes out when the engine starts. You do not have to have an idiot light or a resistor, you can have just a switched 12V running to the #1 terminal and itíll work just fine. (GM it's brown.... ran thru the bulk head connector to the alt charging indicator lamp)

Terminal #2 from the alt goes to the hot side of the wiring system, normally itís spliced into the hot feed leading to the fuse box. This is the sense wire, it tells the alt to produce more or less juice depending on the demands of your electrical system. (Red to an orange fusible link to the bulk head connector into the back of the fuse panel)

The large lug on the back of the alt is the output wire or charge wire and is normally tied directly to the pos post on the battery via a large gage battery cable.

That's it in a nut shell.

Thanks EOD Guy - you helped me out a lot. I appreciate ya.
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