130 amp g 3 Alternator

[bluef250]

Has anyone installed a 3 G Alternator on a 68 or 69 F Series FE truck? What problems did you encounter, particularly with the wiring? What did you do with Amp Meter wiring? I have read that this gauge measures the voltage difference between the alternator output and the battery supply (which creates a current), as they come into balance the gauge zero's out. So even if you generate more power at the same voltage, the gauge should function properly. Thanks

[heep70]

I am not familliar with a G3 alt. What type of alt is that? 130amps thats alot. What do you need all that for? I am just asking.

[willowbilly3]

I don't know what you are refering to as a 3 G either but that size of alternator would need a shunt wired amp guage for sure. My 2 cents on amp guages is forget them and put in a volt meter. A volt meter will tell you all an amp guage can and more, well of course except for amp draw. But if the volts are where they should be then it really doesn't matter what the amps are doing on a normal system.

[bluef250]

The 3 G is a third generation Ford Alternator. I think Ford is up to the 6th generation now. Several Internet sites talk about the Mustang and other Ford folks replacing less powerful alternators on their vehicles. Seems to me the 130 amp 3 G alternator is a good choice. I looked at the single wire, but don’t like the way it works. I want to run a 2-speed electric fan (30/40 amps), H4 lights (4/5 amp per light), some other power hungry accessories (towing a trailer, running a winch, 55 watt back up lights,) and still keep the dual batteries properly charged. Total for the e fan and lights is over 50 amps. My 65 amp alternator would just be big enough to do the job and still keep the truck running without drawing down the batteries, but it is getting old. I have a rebuilt alternator on the truck now. Having a bigger alternator running at partial output seems to be better than having the stock alternator running flat out. The H4 lights are spiky, surging enough that I avoid driving the truck at night. The switch probably is the problem (passing to much current) as others have described. Running the high/low lights through relays should help. Since having A/C installed, the truck runs hot in the summer. A shroud, 7 blade fan, 160F thermostat, and heavy duty radiator do not handle the heat in the 100F+ Arizona summers. Engine temperature in well past the mid point on the gauge. The 3 G should fit physically with a little trimming and with a larger power feed. I am looking at a premade power feed upgrade from PA Performance, but have not decided yet. They also have a “blackâ€Â

[willowbilly3]

If that is the one that has the main current running through spade clips in a connecter (or2) I wouldn't use it. I saw a lot of problems with those overheating at the connecter and melting the wire then the Alternator. I am kind of an old school guy but those old large frame Motorcraft alternators from the late 70s to late 80s are almost bullit proof. While most are About 90 amp, some were 100 I believe, also some were 70 so you have to look if you find one. They use the same external regulator as the small frame and as always make sure and run an OEM regulator and not an after market one. Also if you run a battery with at least a 120-130 minute reserve capacity (forget cca its deceptive) it will take alot of the peak demand off the alternator.
Look on old school buses for big alternators. Some are going to be commercial like Leece-Neville and are good but kind of obscure. Although kind of pricey to repair or replace, the brushless Motorolas had some high output units too.

[bluef250]

If the Ford amp meter was truly an amp meter then a shunt would be needed to pass the current. If it is a voltage meter, measuring the voltage difference, which creates a current, between the alternator and battery then would a shunt be needed? As long as the replacement alternator remains at 14.2 to 14.8 volts then it would create the same current as the stock alternator. Ford installed a 4-amp fuse on either side of the amp gauge to avoid an over current situation. Actually, each end of the 12 to 18-inch long wire between the alternator and the battery connection at the solenoid can be at a different voltage creating a current. If it flows to battery, then the system is charging. If the battery is stronger than the alternator, it reverses and you will draw down your battery. Obviously it works (somewhat), or the amp gauge would not move at all. The way to make the amp gauge move more is to make the gauge more sensitive to the voltage difference.

[bluef250]

Ford redesigned the 3 G and uses a different plug. This is not the one that caused problems. The power comes off a post on the rear of the alternator. Three wires control the alternator. One to the stator, one to the battery and one to the ignition. The engine connection grounds the turkey. Because I hate to be stuck with a bad battery, I run two batteries connected in parallel. I installed a boat duel battery switch to run them. I try to run off one side. I am in process of separating them when the ignition is off so I don’t run both down if I leave the switch in the “bothâ€Â

[bluef250]

In this area we have very, very few junkyards. The closest is an hour away. No old buses just setting about. Besides if you install a speciality alternator when it needs replacing, watch your pocket book. For an alternator, I wanted an OEM unit than could be replaced anywhere. Found the alternator on eBay and I’m having it “rehabed,â€Â

[heep70]

I am kinda old school myself. You seem to know what you are talking about. The bigger alt would be the way to go as long as you know what you are doing.

Not to challange you, but my One-wire alt does just fine running dual batts, Warn 8274, Hella 90/100 watt lamps dims stay on with the brights on (relays installed), 100 watt fog/driving lamps. I have yet to kill my winch battery. No electric fans yet.

I do see were you are going. It would be nice to have that extra bit more.

[bluef250]

Greg, what size alternator are you running? The one-wire alternator is a great idea. The electrical guru’s should find a way to start the alternator without reving the engine to 2,500+ rpm to start the alternator. Most times you need to rev the engine when cool causing unnecessary engine wear. For a hot rod or vehicle that would be used occasionally, this should not be an issue. Another issue, is replacement of the alternator. If the parts are not readily available, you might be stranded waiting to get the part.

[heep70]

Its a 65 or 70 amp alt. You do not need to rev the engine to get it to start charging. Usually when you start a cold engine the choke is closed and the engine is idling haigher than normal. Mine kicks on a 1200rpm. Most alts don't kick on tell 700 to 800 rpm.

Onewire alts are a dime a dozen. Most auto stores have them in stock. You can also get the kits to turn a Delcotron 10-S1 into a one-wire. Summit and Jegs sell the kits.

The alts come in chrome or plane finish. I have also seen 100amp one-wire alts. These are bigger in size also.

This was on of the best mods I have done to my pick-up. I am pretty happy with the results so far.

[Tim P.]

Hey Willbilly3 is there a PT# for a 90amp alt that will bolt right in my truck without any mods? Tim P.

[19felix69]

do an alt. search for a '75 f150 360. i think www.napaonline.com has a 90 amp alt on th first page.