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Alternator Not Charging - FIXED!

nvrenuf

nvrenuf

Holy crap, it's running!
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History: I recently had a wiring failure from a starter wire melting / grounding on a header. The damage: the starter wire where it touched the header, the main 12v wire going to the alternator, the alternator and the starter. As best I can tell, all of the damaged wiring is now found and fixed, the alternator has been replaced.

I'm working with a CS130 alternator, this is the original type for my 91 K5.

The problem: I can't get the alternator to charge. In fact, I'm not sure it ever did (since getting it running). The voltmeter has read above 12 volts but never in excess of 13v, so now I'm thinking I've just been seeing the battery's state of charge not the system charging.

I searched the net and found a lot of diagrams and posts stating this alternator needs a 12v jumper from the 12v stud to the "S" terminal in the plug to make it charge. The original plug was NOT pinned for the "S" terminal so I bought a replacement plug that is pinned to run the jumper.

Ok, the new plug and jumper is installed, I cranked it and it charged roughly 14v for about 2~3 seconds then quit. Now the alternator is not charging at all.

Suggestions? Please speak slowly. :D

Plug markings and diagnosis:
S = battery 12v
F = ign 12v
L = pinned but nothing
P = not pinned

Original plug



Aftermarket plug



Factory manual diagram (it displays upside down in this post, click on pic and it'll display correctly)

:yikes:




I'm lost..... :doah:
 
So is this on the '91? Is it factory wiring? Does it have a fuse link in the charge wire?
You need to talk to $500K5, he has tons of knowledge on this.
 
$500k5? I'll have to look him up, I don't recognize that name.

Yes and no on factory wiring. I removed all the injector related wires but the alt and starter are untouched. There is a fuse link right at the alt, I checked it for continuity and it showed to be good.
 
Oon the original plug the pink wire just goes to an ignition hot.. The brown wire goes to the light in the dash.. If that bulb was blown, that would cause it not to charge.. It has to have resistance on that wire..
 
Oh that's great info!! I've cut out that part of the cluster and sub'd autometer gauges. Suggestions on how to fool it?
 
Also, should I keep the new jumper wire between the plug and battery terminal?
 
Well , I didn't even think of the dash wiring! Sounds like you may have the fix already!
 
Yeah, so I'll find a resistor and add it inline to the brown wire. Is there such a thing as a resistor I can put inline like a fuse holder?
 
So I'm searching for the resistor and they all look like something you'd fine on a circuit board. Do you solder this onto the alternator wire? Seems very vulnerable.
 
Just a heads up, I'm running autometer gauges, and not an in dash light in my 91 and it charges just fine. I didn't do anything to the old TBI harness for the alternator stuff, but it is still plugged into the TBI computer, even though the TBI is gone.
 
You can wire a #194 bulb & socket in-line into the brown wire from the fuse box/ignition that excites the alternator to replace the original one missing from the dash cluster,it has the proper resistance...you can leave it under the hood if desired,it'll only light up with the key on,engine off,and go out once the engine starts and the alternator starts charging,just as the dash light would have..a resistor works too,but they can be damaged fairly easily--its easy to pop in a new bulb if it burnt out..
 
85 Jimmy said:
Just a heads up, I'm running autometer gauges, and not an in dash light in my 91 and it charges just fine. I didn't do anything to the old TBI harness for the alternator stuff, but it is still plugged into the TBI computer, even though the TBI is gone.
Click to expand...
But does it make a difference if the cluster had gauges or lights?
 
On the older square bodies,I'm pretty sure the ones with a amp or volt meter had a resistor in the excitation circuit to make up for not having an idiot lamp ...
 
85 Jimmy said:
Just a heads up, I'm running autometer gauges, and not an in dash light in my 91 and it charges just fine. I didn't do anything to the old TBI harness for the alternator stuff, but it is still plugged into the TBI computer, even though the TBI is gone.
Click to expand...

So is your cluster still plugged up? Is the printed circuit complete? Mine is hacked away with only the fuel gauge hooked up.
 
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