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Discussion Starter #1
Well, I just got the new alternator in. I went with the GM 12 si 94 amp 3 wire unit. Installation was pretty simple. The most difficult part was keeping warm. If you are just doing an alternator swap this would be really easy. I modified my gauge pickup harness as well due to my going with mechanical aftermarket gauges. All in all it was pretty simple. I will be posting a review as soon as I make sure everything is right with it and can write it up.
 

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I for one would like to see it as I just realized this car I'm doing is missing the alt harness and I had planned on the GM 3 wire swap anyway.

Some around here maybe disapointed you didnt take the easy way out but I think you will be very satisfied in the long run. mm
 

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Please do the review/writeup! Lots of people here want to see that!
For curiosity's sake, what application is this alternator? I want to swap in a higher output alternator, but I want to use one that I can get at any Kragen/Autozone/NAPA/PepBoys... you get the picture.
I've actually been investigating the 230 Amp alt from 90s Lincoln/Mercs w/ 6 cyl engines, internally regulated and everything. Pricey (~$200 if you don't have a core) but available anywhere and all that power internally regulated!
 

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This is the next project i would like to do on my car. I would also be very interested in the write up/review. I do not know if i should go with a one wire or a three wire. I have a 1967 xr-7 so i would like to keep the stock volt meter in the dash. Would this mean I would be better off with a three wire? Thinking of swapping in a Powermaster 100 amp chrome alt.
I have not had much experience working on cars so a step by step review would be just what i need.

Thanks and I can't wait,

Jim
 

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Kirkm76 - Definitely do a review on this project. I am at the stage where I have to decide what alt to use. Your solution looks like what I need!
 

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Discussion Starter #6
I am working on the review today. I think the application is like an 84 Camaro with 305, but I'll have to double check that. It is available at auto parts stores though for around 100 bucks. If you really want the 1 wire, you can use this alternator and put in the 1 wire regulator. The 12 si was built in both 3 and 1 wire configurations. Just get an extra 1 wire regulator and toss it in the glove box. The one wire regulator isn't so widely available I'm told. This way when you are in the middle of nowhere and the alt. goes, you can buy one at the local parts store and swap in your spare regulator.

As to my setup, I am doing some tweaking of the system. Currently, the voltage sensing wire is plugged in to the output terminal on the alt. This in essense puts it in a one wire mode since the regulator is adjusting output based on the voltage at the back of the alternator. Thus you get a drop with the headlights on. Not too serious, but I might as well take full advantage of what I have to work with. I am going to run the voltage sense wire from an acc connection in the car. This way when I turn on the high beams I should still get 14 volts at the instrument panel. I experimented with this and the dash turn signal indicators worked perfectly, a first. I just wanted to do some research first and ensure the battery wouldn't get too much juice. I'll have to do a little more testing with the volt meter. As long as I don't blow the battery up or something I should be o.k. as the MSD can take 16+ volts with no problem, but I don't want to stress those old wires.

And as to running your volt meter in the 67 xr-7, I don't see that it would be any easier with the one wire than the 3 wire. You do have to seperate the 2 halves of the 3 wire and rotate it 180 degrees or the pigtail is against the timing cover.

Anyway, if you want to run it like mine is now, all you need is to connect 1 extra wire to a 12 v ignition switched source with a diode in the circuit, so it's really no more difficult than a one wire and this setup fixed 99% of my electrical issues. Only thing left is the turn signal indicators on the dash and I have just about got that one nailed down.
 

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1967 XR-7 install

Jim,
Your '67 XR-7 has an amp meter in the dash. In original fom it works poorly and is not a good indicator of anything. There is not a good way to use it with a GM alternator as it is a shunt type system, not easy to adapt to a GM alternator that is designed to have a volt meter. Possibly you could get a volt meter from a mid 1970's Trans - Am and have the face repainted to look somewhat like a Cougar instrument and go from there.

I am still wondering about the merits of the three wire vs. one wire alternator. Remember, the alternator's output needs to be correct for the battery to get charged properly. Any loads should be at the battery / alternator junction. If you have a different voltage at the fuse block then there is a bad connection somewhere. There should not be a big voltage drop (difference) anywhere in the system. If there is, you have a wiring problem that will bite you later on. The only possible advantage to the three wire alternator I see is the idiot light function.
 

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Discussion Starter #8
volt meter

I found that the cheapo sunpro volt meter will mount behind ahe bezel and lens for the amp gauge. You do have to cut up the back part that holds all the gauges a little though, but mine was already hacked a bit. I see them on e-bay all the time for cheap so you don't have to hack yours up. I did all my gauges except the fuel gauge as none of them worked (someone broke the needles off two of them). Mine is a restomod anyway and the aftermarket gauges were the easiest way to get the xr-7 cluster in. But anyway, it's not difficult to get aftermarket gauges in the cluster and alleviate this issue. I wouldn't hack up your original stuff though.
 

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Discussion Starter #9
Royce,
You are right on the probable wiring problem, that's why I haven't hooked it all up in it's final form yet. I have the dash out so I am inspecting all the wires. I think ideally the sense wire should go to the positive side of the starter solenoid as this is the closest thing to a "main junction" under the hood. As to comparing it to the one wire, the only advantage i've seen so far is the availability issue. Of course, I have never had a one wire, so take that for what it's worth. They both seem pretty simple to hook up though, so I don't really see that as an issue. Unless you get a one wire in a Ford case, I could see that would be a little easier, but even getting it in there is not really a big deal.
 

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CAUTION!!!!!!!! When you upgrade the Alternator to 95 amps YOU NEED to add an extre wire from the Alt output to the starter relay!!!!!!!!!!!!!!! I swapped my original 40 amp alt for a 95 amp Ford alt from a 96-98 or so Taurus or sable, they wire up the same, the connector is a little different. The bad part, I used the stock harness and it couldn't handle the draw with the AC and radiator fans on. The big wire from the alt connects into the rest of the harness roughly behind the license plate. How do I know that? The alt burned that wire (smoke and all) out to where it hooks into the rest of the harness. I had to pull the whole harness out from the right front of the harness and lay it straight out from the left side headlight to repair the harness. I was lucky that's all the dammage I did. BTW I got my alt from a Pick a Part from an early Taurus, connector included, for $40.
Mark
P.S. sorry about the spelling I'm a lousy speller and my spell check doesn't work.
 

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Discussion Starter #11
When you wire up the 3 wire, you don't use the original alternator harness, at least I didn't. I ran a 10 gauge wire from the alt output to the + side of the solenoid. I put the voltage sense wire to the same place (or will anyway), and hooked the turn on wire to a 12 v ignition switched source, in my case the radio since I didn't use that circuit (I like my radio to be on a constant on circuit so when I'm working outside I can listen to Limbaugh without hunting for my keys). You do have to put a diode on the turn on wire. There were a couple of grounds that I gad to relocate that were on the original harness, but that was simple. Is the ford alt. you used internally regulated? If you use the original harness wouldn't you need the old voltage regulator still?
 

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The Ford 95amp alt uses the same wiring and regulator as the 40-60 amp alts. Change the connector and it hooks right up. Also what you can do using the GM alt is on the four wire connector for the regulator there's one wire hot all the time and one that's hot of the key. On the non xr7s there is two wires that go from the Reg to the alt, on the xr7's there's one wire from the reg connector to the alt. You can jump the wire hot off the key to the wire to the alt at the reg connector, then you'll have a wire at the alt that's hot off the key. I've done this many of times when converting to internal reg GM alts.
Mark
 

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Royce,

What if I leave the old dash as is and hook up a volt
meter to the new alternator. This way the amp meter that does not work very well anyway can stay put ,and I do not have to take the dash apart (which I like).
I can mount the volt meter under the dash or any where that looks good right? So if i go with the Powermaster 100 amp one wire I will not be using the stock harness correct? Is wiring a volt meter to a one wire alternator very hard to do? Remember I'm a rookie at this stuff.I need step by step instructions if you know what I mean.

Thanks,
Jim
 

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Discussion Starter #14
The voltmeter would get wired up to something ignition switched inside the car rather than the alternator itself, though I suppose you could hook it to the alt, you would not be monitoring the whole charging system. So if you hook it to the alternator and something happens and the battery isn't charging that isn't the alternator, the voltmeter wouldn't ever indicate the problem. Hooking it up to a switched source allows you to monitor the whole charging system vice just the alternator, or so I figure anyway.
 

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Discussion Starter #15
Mark,
Thanks, I'm going to scope out your hookup using the voltage regulator wiring today. It would clean up the whole install a bit. This is right near my MSD box too so I may also use it as the 12 v turn on for my ignition box. Are these hookups where the old alternator sensed voltage from, if they even did that? Do you think I could run the use this 12 v switched wire to turn on the alternator, MSD box, and run the electric choke. I don't see a problem as all it seems to do is turn on the MSD and the alternator, so that doesn't seem like a big strain and the electric choke hardly seems like a big amp puller. That would clean things up a lot.
 

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A voltmeter can be hooked up anywhere you like, the ideal place would be something with a heavy power draw so you could monitor the voltage to that component. For example if the most power robbing item on your car is an electric fan, the voltmeter could be connected to the feed wire to the fan.
 

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Discussion Starter #17
Dusk-till-Dawn said:
The Ford 95amp alt uses the same wiring and regulator as the 40-60 amp alts. Change the connector and it hooks right up. Also what you can do using the GM alt is on the four wire connector for the regulator there's one wire hot all the time and one that's hot of the key. On the non xr7s there is two wires that go from the Reg to the alt, on the xr7's there's one wire from the reg connector to the alt. You can jump the wire hot off the key to the wire to the alt at the reg connector, then you'll have a wire at the alt that's hot off the key. I've done this many of times when converting to internal reg GM alts.
Mark
Is this the connector that plugs directly into the voltage meter that this ignition hot wire is on? Cos I ain't finding it, but I wasn't trying real hard either as it was cold and rainy. Anyway, am I in the right place. I found the 2 on the schematic that go back to the alt, but no ignition on wire.
 

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Discussion Starter #18
finalizing the wiring...a few final concerns and clarification

power to the field based on the input from the A+ terminal to control the output of the alternator.

That is how I see it anyway. If so, I am pretty close and any changes in my wiring are mostly cosmetic. The sense terminal currently doesn't account for any voltage drop over the charging wire as it's hooked right to the alt. output. Shouldn't be any drop over that short wire anyway. I will move it to the original location though. The turn on wire will be connected to either the old Stator or Field wire and jumpered at the old regulator connector to the old turn on wire. Just to keep it somewhat in line with the wiring diagrams and for cosmetics. I'm also going to turn on the MSD box using this connection. I may run the electric choke off it too. Seems more logical than where I have it now.

Another question. I am told the old wire from the ignition switch to the coil is a resistor wire. I see this on the schematic too. Where is the resistor? Can I remove it and bypass it or do I have to replace the whole wire if I want to use this as a regular 12 v ignition switched source?
 

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On some years it's a link, on some it's the wire. To be honest I don't remember. I would run a new wire just to be safe...

Bruce
 

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On a 68, the resister is the wire it'self. It runs from the conector that the engine harness hooks to at the firewall to the ignition switch. On the XR7 there is a bullit connector behind the guages, that's the where the tach is connected into the power from the switch, through the tach then out to the positive side of the coil (wire from tach to coil is the resister wire). As for the GM alt, here's the deal. There's three wires, one big that's the output to the Batt. Then there's two smaller wires the go into a connector. One is the power supply to the rotor inside the alt, it can have power all the time, this needs to be a good power source. Most people hook this wire to the big output wire. The other small wire is the voltage sense/ turn on the internal regulator wire it needs to be hooked to a source hot of the key, that's why I just jump the wires at the old regulator connector to get key on power to the GM alt. On the 67-68s the stock regulator is inside the engine compartment behind the left headlights. The power feeding the alt should be all right to turn on the MSD box. I don't know about the Choke though, if the choke created enough of a voltage drop on that wire there's a possablity that the GM regulator would percieve that voltage drop on that wire as a low battery voltage and would then crank up the alt and over charge the battery. BTW if you have electric fans on the radiator, control them with a relay and feed the relay (therefore the fans) off the big wire on the back of the alt. The fans will run noticeably faster and could make the difference idling on a hot day.
Mark
 
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