How To: 1G to 3G Alternator Conversion - Vintage Mustang Forums
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post #1 of 67 (permalink) Old 06-09-2019, 08:55 PM Thread Starter
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How To: 1G to 3G Alternator Conversion

1G is the first generation alternator, 2G the second, and 3G is the third. 3G is prized for its high amps at low RPM.
This conversion is specifically for 69 and 70 Mustangs, although the concepts apply to all. Fusible links were first introduced to a Mustang in 1970, and to safely make this conversion you will need to add two fuse links- one as was done in 1970, and a second large fuse link for the new alternator.


In these notes I sometimes have need to refer to wire item numbers. Unfortunately the diagram I got off line for the 70 does not have wire item numbers, only colors. I was interested in the 70 to see how Ford added fuse links. My 69 wire diagram is similar to the 70 and does have wire item numbers, so when I refer to wire item numbers it will be for the 69 and you will be able to see how it relates to the 70 by comparing.


PA Performance sells 3G alternators, a special regulator, the 4 gauge wire needed, and the large fuse links. They have instructions for a ď1G to 3G Alternator UpgradeĒ, but they are generic instructions and dare I say could be hazardous to the health of your carís electrical system- more on that below.


Note 1:
The instructions say to connect the 4 ga. wire, and wire #38 BK together at the alternator. This puts them in parallel. When I complained that if the 150A fuse link opened, whatever took it out would surely melt wires 38, 38A and 38B, they said that if the car didnít have a fuse link then add one. I investigated and told them that 2,377,100 Mustangs made before 1970 did not have fuse links, so there were still a lot of them out there that would have a problem if they followed their instructions and didnít know enough to ask the right questions.
DO NOT connect the 4 ga. wire to 38 BK. Go to note 2 for an explanation.


Note 2:
If you have a 1969 or older car, then add the additional fuse link shown in note 2. This is where Ford added the fuse link in 1970. It isolates the car from the battery, but not the alternator. It can be purchased from picowiring.com, is on page 23 of their catalog and is #5554PT.


With the combination of the 14 ga. fuse link, the 150A fuse link, and NO connection at note 1, two conditions exist:
First, the car will be isolated from the battery and alternator by the 14 ga. fuse link, and second, the alternator will be isolated from the battery and car by the 150A fuse link. PA performance agreed with this reasoning. It should thoroughly protect the systems from a short condition.


If the wires are connected at note 1, then the 14 ga fuse link cannot blow until the 150A fuse blows. Since the 14ga fuse link is trying to protect a 12 ga wire and the 150A fuse link is protecting a MUCH larger 4 ga. wire its obvious that the 12 ga. wires will melt long before the 150A fuse link blows. Again, do not connect the wires at note 1.
Note 3:
The ammeter is a shunt type. It shunts a small amount of current around wire 38A and is scaled appropriately to reflect if the car is charging or discharging. At least that is how it is supposed to work. I donít remember if mine ever worked, and most donít. Since it is no longer in series with the alternator it will not operate properly and must be replaced with a voltmeter. This is a popular conversion and there are services to do so. They will even keep the old scale so it looks stock. Note that even if the connection at note 1 was made, the ammeter would still need to be replaced with a voltmeter.
Note 4:
The whole point of changing to higher amp alternator is for more power. Unfortunately the carís existing wire is undersized and not adequate to run all the new gizmos. You must provide large enough wires to handle the new load, and connect them at the starter solenoid post. This will run them around the old wiring and prevent overloading the old system. To adequately protect them will you need to add a properly sized fuse link and additional fuses after that as needed.
Note 5:
The actual size of the ď150AĒ fuse link is dependent on the size of the new alternator. I elected to go with a 95A alternator because it is the largest size that can still be driven with a V belt. I prefer to keep the stock look and not go to a serpentine system. PA Performance tells me that even the 95A alternator needs dual belts to operate at full amps. This isnít a problem since the power steering belt can be lengthened to reach the second pulley on the new alternator.







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post #2 of 67 (permalink) Old 06-09-2019, 10:34 PM
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Very nice write up. Thanks for sharing and doing such a good job detailing everything
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post #3 of 67 (permalink) Old 06-09-2019, 11:26 PM
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Can you please provide what "NOTE 2" is?
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post #4 of 67 (permalink) Old 06-10-2019, 07:01 AM Thread Starter
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Quote:
Originally Posted by Boxhead View Post
Can you please provide what "NOTE 2" is?

Sure, find where Note 2 is shown on both the 69 and 70 schematics. This is where Ford added the 14ga fuse link in 1970. If you have a 64-69 Mustang you need to add this fuse link. The note tells you where to buy it. It also tells you why you should NOT CONNECT the wires at note 1. The instructions by PA Performance tell you to connect the wires at note 1. I'm telling you not to, and why.

I could make a schematic showing what will happen if the wires are connected and you get a short somewhere in the system- if that will help? Let me know.

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post #5 of 67 (permalink) Old 06-10-2019, 08:18 AM
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So how would you wire a 3G without the PA Performance regulator? It seems sort of redundant to use a regulator on an internally regulated alternator.

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post #6 of 67 (permalink) Old 06-10-2019, 08:35 AM Thread Starter
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Quote:
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So how would you wire a 3G without the PA Performance regulator? It seems sort of redundant to use a regulator on an internally regulated alternator.

Yes they say its necessary. I don't know what is going on internally but you can see that the "field" is connected to their special regulator.

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post #7 of 67 (permalink) Old 06-10-2019, 01:36 PM
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I have the PA performance 1G to 3G. Now Iím going to double check my wiring. I know that my alternator is isolated from the rest of the car, but thatís it. The smal black box in the pic is where my 150A fuse sits. I also am running a PMGR starter, so that should explain the funky wiring on my solenoid.

Very much appreciate your write up!




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post #8 of 67 (permalink) Old 06-10-2019, 02:42 PM
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Quote:
Originally Posted by blueovalfan68 View Post
I have the PA performance 1G to 3G. Now Iím going to double check my wiring. I know that my alternator is isolated from the rest of the car, but thatís it. The smal black box in the pic is where my 150A fuse sits. I also am running a PMGR starter, so that should explain the funky wiring on my solenoid.

Very much appreciate your write up!
Sent from my iPhone using Tapatalk
That's pretty nice box, where did you find it?

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post #9 of 67 (permalink) Old 06-10-2019, 02:59 PM
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I've never seen a 3G conversion that used an external "regulator". But I'm not much for "kits". I've never ever liked fusible links. I'm all about circuit breakers and easily replaced fuses. I use Megafuses on my 3G (and 4G) swaps. The holders I've found on junkyard GM vehicles. THey are OK but I like the looks of that one BlueOvalfan has better.
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post #10 of 67 (permalink) Old 06-10-2019, 05:20 PM
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Quote:
Originally Posted by j persons View Post
That's pretty nice box, where did you find it?


Itís a ron francis distribution box. I pulled out the metal piece inside, and place a mega fuse in its place (happens to fit perfectly)


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'68 Mustang
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T5 manual trans, alum driveshaft, 9" w/3.70 gears
Suspension parts from SoT, Global West, Maier Racing, and a few others. Works for me!
TCP manual rack (love it)
EPAS (Love this the most)
VWW V45 wheels (like these too)
SoT 13" brakes (stopping is good)
And I finally got a paint job!
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post #11 of 67 (permalink) Old 06-11-2019, 08:19 AM Thread Starter
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Quote:
Originally Posted by Boxhead View Post
Can you please provide what "NOTE 2" is?

Its best to show what happens with pictures.
To explain this I need to shift into teaching mode- mind you Iím not a teacher, but I am an Electrical Engineer. First, what is a short circuit, or short? A short is when a circuit has less resistance than intended and is usually near or approaching zero ohms. Lets say that the wire leading to the fuse box gets frayed and connects (shorts) to the chassis.
We will estimate this short is 0.1 ohms, so using Ohms Law, I=E/R =12v/.1ohms = 120 amps. That's enough to melt the 12 ga. wire used to supply all the power to the car in the original harness.
The manufacturers instructions say to install the alternator this way:







This is a guesstimate based on perceived wire lengths from the wire diagram. I wonít bore you with the calculations, but wires 38A and 38B will flow about 54 amps while 38 and the 4 ga. wire will flow about 66 amps.
The 150A fuse link will not open because the amps are too low, but all the 12 ga. wires 38, 38a, and 38B will become a fuse and melt. This occurs at about 38.3 amps in a high heat area like under the hood where wire resistance goes up.






This is the preferred method of installation.
The wires are not connected at note 1 and a 14 ga. fuse link has been installed at note 2. Since the 14 ga. fuse link is smaller than the 12 ga. wires 38, 38A, and 38B, the fuse link will blow and the wire harness will be saved. I would rather be stranded by the side of the road than burn-up the car.






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post #12 of 67 (permalink) Old 06-11-2019, 08:46 AM Thread Starter
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Quote:
Originally Posted by GypsyR View Post
I've never seen a 3G conversion that used an external "regulator". But I'm not much for "kits". I've never ever liked fusible links. I'm all about circuit breakers and easily replaced fuses. I use Megafuses on my 3G (and 4G) swaps. The holders I've found on junkyard GM vehicles. THey are OK but I like the looks of that one BlueOvalfan has better.

A fuse link is the cheapo way to give some protection, and what Ford finally used in 1970. I'm not opposed to using a fuse at all, but don't install a single fuse and leave the system unprotected in 69 or older Mustangs. See what happens above with the simulated short.

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post #13 of 67 (permalink) Old 06-11-2019, 01:28 PM
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Im doing a 2G in my 66 with my 5.0 conversion. Was thing about adding this fuse where the arrow is on the pic. I have removed all of the stock alternator wiring. Do you guys think this would be sufficient?

https://www.amazon.com/dp/B01NBAMIU7..._U89.CbEKTEA0B







Last edited by Anangryford; 06-11-2019 at 01:32 PM.
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post #14 of 67 (permalink) Old 06-11-2019, 02:39 PM
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I would rethink that 2G, those things are a fire waiting to start.
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John

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post #15 of 67 (permalink) Old 06-11-2019, 02:53 PM
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Plus a 2G doesn't charge one bit better than a 1G does at low RPM's, it's just in a tidier package. Not a unit I'd bother with at all. I do like to carry a fire extinguisher though, even though I'm not running a 2G.
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