I have a theoretical idea that might work.

AFAIK, the red wire that goes to the junction box (with all the fuses), and that red wire that goes to the alternator are connected together at the battery, correct?

To rule out the battery, as long as those two wires (+) are connected, you should be able to start your car, then remove the + cable ONLY with the car running. JUST MAKE SURE IT DOES NOT TOUCH ANYTHING, ESP METAL FRAMEWORK. Record the voltage at the alternator.

If you have 13-14v after the battery + is removed, then it would indicate an issue with the battery.
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If you are risk averse, lol, then I would suggest jumping 12v from bat to the redwire pin, and brown wire. See if it causes your alternator to start working. It doesn't make sense for their machines to show it outputting correctly, then on your car it's dead weight.
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Another theoretic test would to be to remove your serp belt, jump the alternator wires (red/brown) or maybe (red/brown&white) to batt (+), and try to spin the pulley. If there is no resistance, there's a prob with the alternator. Because when the field coil is energized, that is what puts a load on the serp setup, creating A/C current as it turns....so by hand you should feel resistance if it's working.

 

I'm by myself, it won't stay running long enough to remove the battery cable to check the volts, I have to remove the alt wires to keep the motor running.

 

Which alt wires do you remove. The plug, or the main power cable?

If you leave it plugged in when you start it, does it die or something?

 

I took the clip apart, I pull the small wire to keep it running. Yes, if I leave it plugged in it only runs for 1 or 2 secs then dies.

 

What small wire? What is the color?

 

if you have 12 volts at both it should be charging. one is the charge wire the big one and the other one when it has 12 volts tells the alt to charge its called the exciter wire . if you have power on the little wire .That is telling the alt to charge. its getting a signal.the little wire should have NO power with the key off did you check that?

 

If you have to remove a field coil wire for it to stay running, something tells me perhaps your engine isn't running good enough to handle the additional load of the alternator. Perhaps a faulty IAC

 

Brn/wht or tan/wht

 

Do you mean the iac motor?? I already replaced that if so. Yeah cause if I need a jump start I have to unhook the cables or it will kill the motor.

 

I don't have a dmm right now, gonna pick one up in a short bit.

 

My buddy is on his way with a dmm to triple check the volts on all alt wires.

 

14 volts from main alt wire in back of alt.

 

its charging

 

It just won't stay running with alt plugged in.

 

is the battery any good? load tested?

 

Yes, hooked up a new battery.

 

Out of a car that runs fine.

 

can you try to unplug your fans .I dont know what to say .you must have a major draw

 

It will run longer if lights, air, radio, and hazards are on. I think it's over charging.

 

if your alt is working correctly then if you pull the positive battery cable, yes the car will stay running. i usually remove the battery cables from a dead battery and hook the jumper cables directly to the now unhooked battery cables to jump start a car. if the battry is dead enough itll pull down the voltage from the car youre trying to jump it with and not let it crank over.

pulling the battery cable with the car running is a great way to test if the alt is fried or not if you dont have a volt meter.

 

he tested it today he said he had 14 volts. did you disconect the fan?? the ac turns on the fans

 

Haven't tried the fan, will do so after work today. I noticed only 1 fan running yesterday though.

 

the fans will draw a lot of power if its shorted. but it should have a inline fuse but some people hard wire them .

 

All fuses are good but I don't trust the wiring, this is a different motor than what came in the car.

 

the fans are on a separate fuse by its self near the battery if there still there and not hardwired.

 

to: oif0709.....I have a very similar sounding problem with my car. Except on mine the alt. puts out 11.8-12.1 at an idle but if if you rev the engine up to about 3 grand or so it puts out 12.3and climing does yours do that?

 

I just had mine rebuilt from an original and I'm waiting for the new wire harness for the alternator to come in tomorrow. I've never had one do that, it should be 14-15 volts though.

 

A few months back I traded my 89 ttop iroc for a 91 z28 conv. Needs paint and the motor in it now is some old truck motor with 882 heads(junk). Well the first time I drove the car the serp. belt broke and the water pump was leaking badly. So i got new belt new water pump put on the pump and then belt (snap) there went the damn bracket for alt and ps pump and also broke ear off alt thats on top where bolt goes. I got new (3345611 ultima) from oreilly auto parts well put it on car(not charging) tried another today not charging either. ideas anybody???????????? Oh maybe one day when i get some of the bugs worked out where i can drive it down the road them im going to borrow intake setup from a buddy AND SPRAY THE BOTTOM END OUT OF IT. maybe 300-500 shot. If i can I will put it on youtube

 

Where can I get a good engine wire harness, and a good frame shop by KCMO

 

putting a new wire harness to finish EVERYTHING under the hood, nothing has more than 100 miles on it, need a little help and tips on changing it, please help

 

Just a fyi , Check for voltage drop at the battery connections, Long story short.... don't overlook the crimped wires at the battery, starter and fuse link bar , some of the problems others have posted sound like bad connections within the battery cable where the alt wire connects. I know it's an older post but it shouldn't be overlooked. They may feel tight and look good but have a high resistance that can cause alternators and batteries to look bad.

 

I would hope over 2 years later he has it figured out....lol

 

I know....I've been going through forums looking for problems like mine, low to no charge during warm-up(sometimes normal charging). Figured it might help somebody else?

I wasted so much time on a bad connection that looked good and had no signs of corrosion

 

You are awesome, this is why my alternator wasn't working on the car ive been putting together for 5 years. Thanks!

 

an old post helps after-all......just saying....good luck

 

that is weird normally its a fuse but im glad that you figured it out

 

 

My 1991 Chevrolet Camaro Rs was having the same problem. I got a new battery and change out my alternator 2x. After basically giving up on it for a year I then check all fuses located at the driver side underneath the steering column. Comes to find out the fuse for the C/H fan didn't have a fuse in it. Now that I had put a fuse my voltage reads 13.8-14.2. So far my car not losing power. Hopefully this helps a little.

 

Having the same issue with a new/remanufactured alternator not charging, I'm using an alternator for a 7.4 454, same electrical connections as the factory 91 alternators, it's the mounting points that I needed.
Both the 91 454 and the 91 350 use a CS-130 alternator. Are all CS-130 alternators internally wired the same? Is there a difference in the voltage regulators?
Fuses are good, all wiring associated with the alternator has been double checked, voltage is where voltage needs to be I even jumpered the battery post on the alternator to the "S" pin on the connector as suggested by Tuned Performance in post #2, still the alternator was not charging. I've had this alternator tested twice, once a few months ago and the second last night, both times it past at my local AZ.
Random thought... the adapter plug that is used for the testing machines, is there a different alternator adapter plug for a 1991 7.4 454 big block and a 1991 5.7 350?

 

Maybe when you're guys are hooking up a power why not unbolt the alternator bolt where the "alternator ground to the motor block" and run a ground wire that goes to your battery that way while the positive terminal wire running to the red on the alternator(alternator charging point)to the battery's positive terminal post it should be it's own unit charging