How to 3G Alternator

[Helirich]

If your looking for a good alternator upgrade, this is it. I've written quite a book here. If you want the basics and are not interested in how I came to choose this alternator, just skip to the bold #1 and start ordering parts. i would recommend at least go to the bold “The Test” and preform this test on your car. If it passes, no need to upgrade. For anybody else that wants the whole story, read on.

The Event

I was driving my 1990 Ford Bronco down the road in 2011 in Houma, LA. (I was there for work) My wife called and I pulled over to talk. It was 95 in the shade and I just let the truck idle with the AC on max. One thing led to another and I was talking there for aprox. 40 minutes. The truck started to run rough and the AC was not blowing so hard. About that same time, I noticed steam/smoke coming from the hood.

I got off the phone and found my temp gauge hot and the volt gauge reading around 8 volts. I guessed the belt came off, but decided to give the throttle a little rev to see. Amazingly, the engine reved right up and the volt meter read 13 volts. The AC started blowing hard again. Now I figured that my aftermarket E-Fans had quit and i needed some air through the radiator. I pulled out on the road and got up to about 40mph. In half a mile everything was fine. When I got to the hotel, I let it idle and checked under the hood to find the E-Fans working great.

The Explanation

I knew a guy (that has since passed away) that rebuilt alternators, starters and generators for a living. (a lost art) Anyways, he said theres no mystery to my event. He figured my aftermarket cooling fans probably draw 20 amps each. My stock 75 amp alternator is fine while Im driving, but only produces about 15 amps at an idle. The rest is coming out of my battery. If I sit too long, its going dead. As it does, the E-Fans will start to slow down, causing more trouble.

The Answer

I figured I needed a higher amp alternator. My friend said that was not the whole answer. He went on to say, the problem is even a typical 150 Amp alternator is not going to be enough at idle. You need the 3G.

The Ford 3G

He continued the Ford 3G is the best alternator Ford ever made. in fact, it is arguably the best alternator any major manufacturer has ever made. There are custom and special alternators that are better, but if you want common, inexpensive, reliability, the 3G is it. Ford is now up to 6 or 7th generation, but it appears accountants designed the newer versions. (they are not better). The 3G shines in the one area you need. A typical 110 amp alternator will produce 25 amps at idle. The typical 110 amp 3G will make 50 amps at idle.

The Test

Start your car and let it idle. It doesn’t have to be fully warmed up, but should be idling normally. Turn your AC on high. (Make sure your e-Fans are on.) Turn all your lights on, including high beams. Turn your radio on. Take your multi-meter, set to volts and get a reading.

If it reads 12.6 volts or better, your golden. (go have a drink)
If it reads less, not so good. (you might consider this upgrade)
If it reads less than 12, you probably should be doing something.

I did the test on my truck and it read 11.8 volts. I did the same test after installing the 3G and it read 13.2 volts. i did the test on my Delorean and it was 12.1

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1. Sourcing the 3G

They made several versions of the 3G. Here you see a wide pivot mount on the right and a narrow pivot mount on the left.

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They also make side mount 3Gs. Note they have no cooling fan. (its inside) All 3Gs have the 3 double bars cast in to the front with holes. (some 2 holes and some 4 holes) If you want to look in a junkyard, there are lots of Fords from the 90’s that have them. (But not all) If your like me, you donÂ’t want a used alternator. So you can buy them brand new at your favorite auto parts store with a lifetime warrantee.

The one on the left is the one I used for the D because theres not much room for the wide mount. That is unfortunate because Ford made a wide pivot version with a V-pulley. My receipt got ruined in the shop, but I recall, It was from an 98’ Ford Taurus with a 3L motor. it was about $150 bucks. (might be a core charge in there)

You can see the new plug I got from ebay in front. The 3G on the right (for my truck) has a junkyard plug. They are easy to find and all you need is the plug and maybe 4” of wire. If you order off the bay, you want a plug for a 2G,3G,4G. It has unique D shape socket to it. Ford also has a flat plug for their old alternators. (don’t mistakenly get it)

Set up

Disconnect your battery.
Remove your old alternator and its mounts.
I would remove the upper muffler mount for access.

3. Pulley

Since the 3G I got had a serpentine pulley, I removed it and took the stock pulley off my original alternator. The nuts come off with an impact easy and the pulleys pull off by hand. the threads were different, but the shafts was the same diameter. i had to put a thick washer on before the pulley so it wouldn’t scrape the housing.

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4. Main Pivot Mount

This alternator mounted totally different from stock. This is one thing you might want to look in junk yards for. Im sure you can find something that could easily be modified to fit. I was in a hurry and made mine out of a piece of angle iron I had lying around the shop. I started by drilling the three holes.

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In order to line the belt up I had to do get accurate measurement of the mount hole to the pulley. then I welded the pivot mount tabs on to get the new pulley at the same distance. Of course, I should have cut the angle iron a 1/4” longer. but I got it welded. After installing the mount, I had to trim my upper muffler mount to make it fit. You may be able to engineer you pivot mount so that is not required.

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5. Belt Adjust Mount

The adjustable mount tab is set up for a big bolt. (like 3/8”) I don’t like a bolt and nut in this location because its hard to hold tension on the belt while your tightening the bolt and nut. So I tapped the hole for 3/8” NC heli-coil. (the hole is already the right size) Installed a heli-coil and It was ready to mount.

The stock slotted mount was very small. I had another larger one off of some other engine that i used. This is another item you can easily get in a junkyard. I believe they sell them at Summit also.

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The stock location for the slot bar was not going to make it, so I cut a small piece of angle iron and used the two muffler mount bolts to hold it.

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6. Electrical

All the plugs I’ve seen have green, white and yellow wires. You need to strip the green and yellow wires and crimp a (1) ring terminal on them. The white (center) wire is not used. The ring terminal must be sized to go on the charge post on the alternator.

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The only other wiring is the charge cable. You have several choices here. You could run your cable to the battery, starter or the jumper cable stud. You might be able to just bolt the OEM cables to the charge post. (It would be hard to stack them up on there.) I used an old golf cart cable I had. It was 2GA with small ring terminals already and i ran it to my jumper cable stud.

I bolted my old cables together and wrapped them up with electrical tape. Then I tied them up to the frame.

Note, wiring like this has pros and cons. Your alternator light will not work. But, your alternator light will not burn out and shut down your alternator either. Basically, you must rely on your voltmeter to know your alt is working. On a good note, you will never see your voltmeter below 13 volts. so you don’t need to guess if its above 12.5.

7. Closing Points

After all was in and tight, I hooked the battery back up and started the car. Of course, I had to do “The test” again.

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View from top.

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I did this in one day and drove the car to a party that night. I might not have everything just right, but i can go back and do it again now that i have 1.25 mega watts available. If anybody decides to do this upgrade, please post pics of your mounts.

[Ron]

Your light should work if you:
Connect the aftermarket pigtail's (I), Green wire (OEM- Light Green with Red stripe), to the DeLorean's (L), Brown with Yellow stripe, wire.
The (S), White wire (OEM- White with Black stripe, or Black with White stripe), would go to the one terminal socket next to the 3G alternator's main (B+) terminal.
The (A), Yellow wire (OEM-Yellow with White stripe), can go on the main terminal as you have it, but it's better to put it as close to the Battery(+) post.

The voltage, after allowing the alternator to replenish the battery after cranking the engine, should be 13.5V to 15V (13.5V to 14.7V for wet batteries).
FWIW- Many aftermarket alternators fall below specs because their pulley is to large. (The DeLorean's drive pulley is much smaller than most.)

[Helirich]

I figured there was a way to make it work. I don't care that much and I don't even want it if it can shut down the alternator.

As far as the pulley, I would like a slightly larger one. I used the stock belt and larger pulley would bring the alt closer in. Also, there would be more "wrap" for more traction. I have to have this very tight to stop it from squealing.

Edit, as an update, my Bronco's 3G failed about three weeks ago. So it lasted about 10 years. I got a new one at advanced auto under warrantee. I'm happy with that.

[JohnnyK]

I don't care that much and I don't even want it if it can shut down the alternator.

This is why when one wires in a 3G alternator (or any alternator), there is a parallel path with a resistor in it.

[Helirich]

This is why when one wires in a 3G alternator (or any alternator), there is a parallel path with a resistor in it.

So if I understand what your saying, the alternator light won't shut down the 3G? If that's the case, I will look in to it.

[Ron]

I figured there was a way to make it work. I don't care that much and I don't even want it if it can shut down the alternator.

As far as the pulley, I would like a slightly larger one. I used the stock belt and larger pulley would bring the alt closer in. Also, there would be more "wrap" for more traction. I have to have this very tight to stop it from squealing.

Edit, as an update, my Bronco's 3G failed about three weeks ago. So it lasted about 10 years. I got a new one at advanced auto under warrantee. I'm happy with that.

The Like most modern alternators and rebuilt alternator regulator replacements, the 3G has a self exciting regulator. The alternator will come on when its shaft reaches a sufficient RPM. The green wire should be switched and come on with the ignition through the bulb. You have it wired hot at all times. Putting a 540Ω resistor in parallel with the bulb, as many stock setups have, ensures that the field is excited in case the bulb blows (or low RPM).

[JohnnyK]

The alternator lamp is part of the excite circuit. There is (ie: you have to add) another circuit in parallel with it to continue to excite the alternator if the lamp becomes an open circuit.

[Ron]

The alternator lamp is part of the excite circuit. There is (ie: you have to add) another circuit in parallel with it to continue to excite the alternator if the lamp becomes an open circuit.

It won't turn off. Even the older integral alternators would continue to put out, once excited -- But it might not come on.

[JohnnyK]

It won't turn off. Even the older integral alternators would continue to put out, once excited -- But it might not come on.

That is what I meant (by Continue I meant continued use of the car). The OP used the term Turn off, not me.

Thanks

[Ron]

That is what I meant (by Continue I meant continued use of the car). The OP used the term Turn off, not me.

Thanks

lol...I think we are on two different pages.
I mean that with or without the bulb or resistor, the alternators with integral ("built in") regulators will continue to put out, once excited, I.E., no need "to continue to excite the alternator".