1991 4.0 Alternator Swap

[kinville]

Well I tried to search for the answer to this problem, but not coming up with much. I need to step up to a higher amp alternator, however 91 4.0s have a weird way of being wired into the charging system in that they dont have a place where you would connect a ring terminal, but instead have another little pigtail plugged in. A very innefficient way of transfering power to begin with, and only 80amps on top of that. I believe that is also why almost all aftermarket alternator list compatible years starting at 1992, but nothing earlier... So my question is if I were to purchase an alt compatible for years 1992-2001 as most of them are, can I just cut off the pigtail and and use ring terminals on there and everything still work properly?

 

[shadetree]

A connection is a connection as long as it is clean and solid.shady

 

[yoyodyne]

Sounds like you have a 2G alternator, the later model 3G swaps are cake to do. Only 3 connections to make. You can use a junkyards harness.

 

[Sasquatch_Ryda]

Grab a 130amp alternator out of a 4.0 OHV explorer and the wiring harness, it'll bolt right on and the harness will plug right in.

 

[igiveup]

Hello

I did a 3G alt upgrade on my stang for $50 from junk yard and Princess Auto. My volts at idle is 13 and higher rpms its up to 14-14.5 volts. Its worth every penny. Next summer when I upgrade to cfi on my 2.8l B2 I will be doing it again. I just have to bypass my amp meter. My T-Bird alt is starting to act up and I will be doing it shortly. Theres alot of info out there to help you.

igiveup

 

[kinville]

Alright, so I have a 3G series alt in there now... the swap wasn't too difficult... Just cut up the old harness to make it fit for the new alt. Bought it from DB Electrical, and is rated at 105/idle and 160/1200 rmps. However it really hasn't solved my problems... I understand that these ground themselves by the bracket, through the block, from the block to the chassis, and from the chassis back to the battery. I ran 1/0 awg from the neg batt terminal to the chassis, from the pos batt terminal to the alt, and then ran a ground directly from the bracket where the alt mounts to the neg batt terminal. So that should all be good it would seem. However, even the slightest draw causes voltage drops! Rolling up my window (power windows obviously) with nothing else running (headlights, a/c, stereo, etc.) causes signicant voltage drops. And if say my headlights or heat is on, I can hear the blower motor slow down and the see the lights dim... I just don't know enough to figure this out...

EDIT: With no draw, DMM reads 14.4 at idle, batt rests at 12.6 Even the turn signal on will show a slight voltage drop... which turns into a bit more of a drop with a few things on.

 

[kinville]

Anyone have thoughts on this?

 

[kinville]

Now its reading 12.27 at rest... Guess its the batt? Is it possible it was going out before it would show any signs on the dmm? Its a Diehard platinum and less than a year old...

 

[Ranger#1]

runn a jumper form the alt braket to ur batt i did it using 8 ga power wire i did notise an increace in voltage and less draw with acc on