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Ford G Series Alternator Upgrade

Parts and info to get the upgrade done

This is not a new upgrade but one that does have it's merits with the addition of all sorts of power hungry stuff to our street rods. The stock alternators work well under their stock applications but when you need more power this is the way to go.

The 3G alternator comes in outputs all the way to the 130 amp version. This is the one to get. Now it does come in a couple of flavors. Here are the details. The three choices are a 7 inch pivot mount, an 8.25 inch pivot mount and a side mount with horizontal bolts. The ones I will concentrate on here are the two pivot mount types because they closely resemble the factory style mount.

The connectors for this upgrade can be sources from a variety of places.

Alternator Connections for Other Years: On your 84 external voltage regulator, you have the following: F, S, A, I. Unplug the wiring harness going into the external voltage regulator. Either splice into with your new wire or make a blade connector that will go into the old wiring harness. You will need to tap into two of those wires: The F will not be used. The S will go directly to the I on the 3G. The A will go directly to the A on the 3G. The I will not be used.

Looking at it from the 3G viewpoint:
The BAT goes to the inline fuse.
The stator connector goes to the S connector on the 3G.
The A connector goes to the A wire on the old wiring harness.
The S connector goes to the stator connector on the back of the 3G.
The I connector goes to the S wire on the old wiring harness.
The connector you will need is a Conductite #85843.

Note:If you don't want to fabricate your own adapter set up PA Performance has a set of conversion adapters and pigtails available. PN #462802C covers you if you want to keep the externally regulated factory wiring and PN #462802B if you are not.

Low Budget? Looking for a used one? Here's Where to look.

Here is a list of vehicles that have the 3G alternator, most are 130A, but some might be 110A:

If you have a 66-86 or anything with v-belts, you'll need the pivot mount style unit with 8.25 inch ear spacing alternator. These can be found on some 90, any 91-92, and some 93-99 non DOHC Ford Taurus. A wide-eared Taurus alt will ONLY fit a 302 or 351W if it is a V-belt setup since it's wider than a serpentine one. You may also be able to use a Pivot Mount with 7.00 inch ear spacing from an 87-92 serpentine setup on your v-belt system. The Pivot Mount w/ 8.25 inch ear spacing can be swapped into:

87-92 302 or 351W have a 2G alternator. This is an early serpentine style. This can be upgraded with a 7.00" pivot mount 3G alternator. Minor bracket clearancing may be required.These can be swapped into: 1987-1992 Broncos/E-Series/F-series trucks and 1966-1995 Mustangs. This can be found in the following cars:

The only mechanical issue is the mount ears. The units use metric threading and some models of this alternator don't have threads in one of the mount ears. Not a big to do but a quick hardware fix with a metric bolt and nut combination.

For pulleys, you can either re-use your old one, which sometimes you may need a very small washer to use as a spacer if it rubs in the 3G case at all, or you can get a different sized one. It all depends on your needs. A smaller pulley will spin the alternator faster at idle to create maximum output. A larger pulley will allow the engine to rev higher without driving the alternator too fast. Large 3G alternators are safe to around 15,000 Alternator RPM max. Again, Alt RPM = Engine RPM x Crank Pulley Diameter divided by Alt Pulley Diameter.

Some salvage 3G pullies to consider

If you do not get enough output voltage at idle, replace the standard 60mm pulley with a 1 3/4” (44mm) overdrive pulley from Auto Specialties.

Auto Specialties Performance
13313 Redfish, #104
Stafford, TX 77477
(281) 261-5811 /(281) 261-5715 / Fax (281) 261-5811
Order Toll Free 24/7 1-877-928-8678

It's easy to monitor voltage on the go, make a cable that connects your DVM to the cigarette lighter and watch it under all conditions. The voltage will drop off when the engine/alternator get warm; this is normal. When the load increases, i.e. electric fan comes on or you turn the AC/heater blower on, the voltage will normally drop. It would be nice to keep the voltage at idle above 12.6V, which is the voltage of a charged battery, otherwise you will be drawing current from the batter (discharging it) instead of from the alternator.

Now with all this said and done we have more juice but one other consideration is to the main charge wire. It is highly recommended that you upsize this wire to a suitable size in order to handle all of this new power. The following table is a good guide to making that size selection. It's never a bad idea to go oversize here!

Recommended Charging Cable Size

AMPS Up to 4 4 - 7 7 - 10 10 - 13 13 - 16 16 - 19 19 - 22 22 - 28
35 - 50 12 12 10 10 10 8 8 8
50-65 10 8 8 6 6 6 6 4
65-85 10 8 8 6 6 4 4 4
85-105 8 8 6 4 4 4 4 2
105-125 6 6 4 4 2 2 2 0
125-150 6 6 4 2 2 2 2 0
150-175 4 4 4 2 2 0 0 0
175-200 4 4 2 2 0 0 0 00

How to Test Your Alternator and Voltage Regulator

You can check the functioning of the alternator with a voltmeter. Put the voltmeter across the battery terminals. With engine off, fully charged battery is 12.5-12.7 VDC. With engine on, all accessories off, it should be around 14.6 VDC when engine and alternator are cold. As you start turning on accessories (lights, A/C, A/C blower) voltage will drop. With stock 2G, 75A alternator, voltage will drop below 12.7 VDC. With 3G, 130A alternator, voltage will not drop below 13.0 VDC.

NOTE: There are 2 reasons for the drop:

1) As the temperature of the alternator increases, the regulated output voltage decreases. This is due to a negative temperature coefficient of the voltage regulator (approx. -10mv/�C.). If the alternator has a temperature rise of 100�C (68�F to 248�F), the regulated voltage will decrease by 1.0V,

2) As the alternator load increases, the regulated output voltage will decrease. The 14.6V regulator output is at 0% load. At 6000rpm at 90% load, the voltage will decrease 0.3V. After the alternator reaches operating temperature (which is hot!) and you put a heavy load on it, you will see a voltage output of about 13.0V. As long as the alternator output voltage is slightly higher than the full charge of the battery (12.5-12.7V), the alternator (not the battery) will be supplying the current to the vehicle, and therefore, you are neither charging nor discharging the battery.