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Discussion Starter · #1 ·
Every tech article I read on hooking up a three-wire alternator (SI) talks about the color of the factory wiring, and the hookup to the warning light in the dash.

The only factory wiring in my car is in the steering column harness. The rest I made myself, so colors, bulkhead connector, etc. are all completely different.

I have a 100-amp Powermaster alternator that works fine as a One-wire, but I want to hook it up for the remote voltage sensing that I've heard so much about lately.

BTW, Powermaster One-wire alternators are supposed to be able to be hooked up using either one-wire or three wires, so it's a "plug-and-play" (supposedly) to a vehicle originally equipped with an SI.

The Regulator is plugged off with a rubber cover. The two "R" terminals are numbered "1" and "2".

edit: In this article, the voltage sensing wire is the brown wire, which goes from the #2 terminal (on my alternator) to the main junction. I guess this is what I have to hook up.

Do I need to do anything with the other terminal? Do I have to have a warning light for this to work? Or will initial excitation continue to occur when I rev the engine above 1000 or so?
 

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Discussion Starter · #2 ·
Additionally, the sensing terminal isn't internally jumpered to the main output terminal on the Powermaster alternator. I just checked it with my meter to be sure. There is not 12 V at either regulator terminal.

I have run SI alternators in the past with a jumper from the sensing terminal to the main output post, "mimicking" a one-wire alternator.

I'm not sure what's different on the Powermaster alternator, but something must be different internally to allow excitation without the regulator wiring attached.
 

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basically the color doesn't matter
as for the alternators all that does matter for the externally regulated style is that the field wire from the reg gets hooked up to the field of the alt
and the stator outtput goes to the relays
then to have the hot connected to both the alt and (through a fusable link)the regulator
then a switched wire to turn system on
the internally regulated ones yes just jumper the output to hot then you just need power to switch the field on
 

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I upgraded my Powermaster 100 amp 1 wire to a 3 wire, I just removed the rubber grommet and wired in the 3 wire alternator kit I bought from Mad Electrical
They provide the diode, wires, heat shrink tubing, and diagram to do it right. I bought extra heat shrink tubing at Radio Shack and encased the two wires in tubing and then draped it over the driver side to the driver side fender and then soldered the diode inbetween to the brown wire that runs to my idiot light, the other wire runs to the Mad Electric Power Post near my radiator along with the Mad Electric Headlamp Relays to run the headlights directly off the new power post.
 

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Discussion Starter · #5 ·
Originally posted by TOM'S 68 CONV:
basically the color doesn't matter

<snip>

the internally regulated ones yes just jumper the output to hot then you just need power to switch the field on
Thanks for the reply, Tom.
I really do appreciate your taking the time to answer.

You're right, the color doesn't matter. I wired the car myself and used whatever colors were available at the time. Everything works great with the different colors and a few of the AWG sizes increased.


Your answer is correct. I did a lot of research in the past few hours and found the info that I needed. The only thing with "power to switch the field on" is that if you use the ignition to switch it on without the warning light, the car won't shut off. Sure, a separate power supply would work. I thought about using a diode, but one of the sites I visited said that the system wouldn't like the voltage drop across the diode. I also thought about using a relay, but I already have 7 relays in my harness. I'm running out of room to mount the things.

I thought to myself, "What the hell. I have an extra hour or two today". So I decided to just mimic GM's original design (with my own "personal touch").

Brian, I got some of my info from Mad Electrical's site, so I'm familiar with their products. Good stuff, but I don't like spending money on things like that.

I got myself a plain old red light for my dash and connected it in series between the ignition switch and the field. I also got a plug for the alternator so I wouldn't have a couple of 1/4" female spade connectors hanging off of my alternator. I wired the other terminal to the main junction that I use to power my fan and headlamp relays, rather than the junction I have the alternator output hooked up to. Since both junctions are equidistant from the battery, I figured I'd favor my high-current loads.

Once I hooked it all up, I tested it. I now have an Alternator Warning Light. I no longer have to rev the engine to excite the field. And I have a full 14 volts showing on the voltmeter with all loads switched on at idle.

With the one-wire setup I had to rev the engine to excite the alternator. I had no warning light (though I always keep a close eye on my gauges), and voltage always dropped on the gauge when I switched on my headlamps, high-beams, or electric fan. I also always noticed a slight flicker when any additional load was applied (turn signal, brake lights, whatever).

So I can attest from personal experience that the three-wire setup is far superior to the one-wire, no matter how powerful your alternator is.

Total cost for converting the Powermaster alternator to three-wire operation was just over $5. That includes the warning light, wiring, terminals, and alternator plug.

I'm sure Mad Electrical's product is excellent, but I'm pretty good at designing my own stuff once I know what's required.

Thanks for the help guys!
 

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The blocking diode wouldn't have hurt Chad. That's the recommended fix to prevent run-on on MSD boxes. Those things take so little current to operate, without a blocking diode, the alternator continues to feed the ignition through the idiot light.
 

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Discussion Starter · #7 ·
My MSD isn't continuing to run, so I guess there's enough resistance in my warning light. Haven't measured the resistance in it, but it works, and that's all that matters.

I carry an electronic "field survival kit" with me which includes a whole bunch of resistors, diodes, transistors, triacs, and other stuff. So if I were to have a problem with it, I can easily cut a wire on the side of the road and solder a diode into the circuit.
 

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Discussion Starter · #9 ·
Go to Radio Shack and get one of those butane soldering irons for around $15. Failing that, get an inverter for around $60 at Wal Mart. Both work fine for soldering on drilling rigs with no generators running (yet). :D

When you work out in the middle of the wilderness, (a hundred miles from "nowhere") you have to "improvise". :D

I figured a bloody pirate would know this better than anyone. ;)
 

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That's cool Chad, it's nice to hear a real world test between the 1-wire and 3-wire alternators.

I think a 1-wire works just fine without any high current accessories but once you get into electric fans (especially the 40A fan you have) and other high current loads the 3-wire is the only way to go.

You also picked the correct spot for the voltage sensing. It should always be connected to the junction block where the high current loads are connected.

I personally like the idiot light and the way you don't have to rev the engine to get the alternator to start.

Peter
 

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Originally posted by cjlandry:
I figured a bloody pirate would know this better than anyone. ;)
Reminds me of the the time where I had the family bail out of a Bonneville due to a little engine fire that smoked up some wiring. A few scrapes and twists on the wires, it was back in the car for everyone. Didn't score many points that day. "Is the engine gonna do that again Dad?"
 
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