3g alternator upgrade


Mar 5, 2021
vancouver bc
hey guys new to the forum. Just picked up a 92 notchback. I had a question about doing a 3g alternator upgrade. I found a 130amp 3g alternator off of amazon and also a wiring kit. My question is I am running electric fan, under drive pulleys, sub amp alarm etc, I plan on doing a fuel pump upgrade down the road. I have read that upgrading my alternator and running these underdrive pulleys basically defeats the purpose of the 3g alternator upgrade? What should I be doing here? Remove the underdrive pulleys, swamp them out? let me know, would be greatly appreciated thanks
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wanna catch the space herp
10 Year Member
Sep 1, 2010
Kearney, NE
I would not swamp them out. A gator might choke on them. eBay or recycling will be a better plan.
There are at least two how to threads under electrical you will want to read.


Put lubricant all over the balls
Mod Dude
Feb 18, 2001
Quick, simple answer: Put the stock pullies back on for best results

Long Answer: You can make the pullies work, but you'll need to make sure all the other systems are in good working order. The alternator charges based on RPM and outputs the required amperage as necessary. Alts have a min RPM to create a certain number of amps and each one is different. If you intend to run underdrives, you'll need to take the alt pulley and throw it in the trash. Then find the smallest alternator pulley you can find. ASP sells a 1 7/8". The small alt pulley will compensate for the underdriven crank. It might be enough of an RPM bump to allow for full charge at idle. You'll also want to make sure your cooling system is in tip top shape. Pullies don't cause the car to overheat, but they can expose weakness in the cooling system which will lead to overheating. Also, the lower RPM does mean reduced A/C performance as well (if you have functional AC)

With all that said, I ran UD pullies with an E fan and 3G130A alt for nearly 20 years without cooling or electrical issues. I was able to make it work, but in my latest rebuild I put the stock pullies back on. I was going for reliability over Horsepower. Better cooling and charging capability and AC performance are more critical to me these days
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Wasn't a pretty sight...and I've got big hands
SN Certified Technician
Mar 2, 2015
When I ran underwrite pulling I used the 130amp alternator and alternator pulley off of a 94 escort. Was smaller than the fox one. Had a sound system 2400 watts, 3 farrad capacitor, and a jeep cherokee electric fan. No charging issues. Got rid of that set up years ago.