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'83 K5 Alternator not charging

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Rick465

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OK, I am sure somebody has posted a fix on this...I probably missed it. Anyway, My alternator on my '83 K5 350 stopped charging. With the truck running and the battery disconnected the engine continued to run but the alternator was overcharging, approx 16v. The alternator was about 2 years old. Had it tested and they said the regulator was going out, so they replaced it with a new one. I put it in and get no charge. The plug on the back was looking a little crusty so I changed it. Still no charge. Moved the ground wire to ground directly yo the body. Still no charge. Put a 10ga wire directly from the pos side of the battery to the stud on the back of the alternator (bypassing the fusible link). Still no charge. I am getting battery power at the alternator approx, 12-12.6v. It goes down charge when I turn lights, AC etc on. I have continuity on all thee places I can figure to check. There's, of course, no fuse in the fuse box for this. It's all in the fusible link. (I did put a fusible link in the wire going from the battery to the stud)
The alternator is not getting excited, right? My meter says there is battery power in 1 of the wires in the plug and nothing in the other plug, with the key on. It should have power, if the fusible link is burned out, but the direct connection to the battery should have fixed that, right?
I am not the sharpest egg in the drawer...what am I missing?
 
did they test it after they put a new regulator in?

edit: I read this as you took it some place, they tested it, said regulator was bad and put a new regulator in. or did you mean they tested it and said regulator was bad and exchanged alternator? either way, has the "new" alternator been tested?
 
Last edited:
Rick465 said:
OK, I am sure somebody has posted a fix on this...I probably missed it. Anyway, My alternator on my '83 K5 350 stopped charging. With the truck running and the battery disconnected the engine continued to run but the alternator was overcharging, approx 16v. The alternator was about 2 years old. Had it tested and they said the regulator was going out, so they replaced it with a new one. I put it in and get no charge. The plug on the back was looking a little crusty so I changed it. Still no charge. Moved the ground wire to ground directly yo the body. Still no charge. Put a 10ga wire directly from the pos side of the battery to the stud on the back of the alternator (bypassing the fusible link). Still no charge. I am getting battery power at the alternator approx, 12-12.6v. It goes down charge when I turn lights, AC etc on. I have continuity on all thee places I can figure to check. There's, of course, no fuse in the fuse box for this. It's all in the fusible link. (I did put a fusible link in the wire going from the battery to the stud)
The alternator is not getting excited, right? My meter says there is battery power in 1 of the wires in the plug and nothing in the other plug, with the key on. It should have power, if the fusible link is burned out, but the direct connection to the battery should have fixed that, right?
I am not the sharpest egg in the drawer...what am I missing?
Click to expand...
First off I would check if the alternator has an exciter plug, get battery power on it to excite it while engine is running.
If it doesn't work, go get the alternator tested.
 
They replaced the entire alt. They didn't test it. Why would they...It's new. UGH
I did run power to the exciter wire and got nothing.
I'll take the alt off...again...and get it retested. I'll let y'all know after I magically create enough time to get a verified working alt back in. THANKS!!!!!!!!!!
 
Long shot… also check the battery, dead cell will make problems for you.

Not saying thats your problem but its worth looking at.
 
something is not right here. This is an easy system. If the alt has battery voltage and terminal 2 does also, it should charge.
Now as Max mentioned your battery condition could be effect your charge rate. If you can charge that battery up to 12.6v then do the alternator test
make sure your battery ground is good at the block, if it is on the alternator upper bracket, make sure all 3 bolts are clean and tight.

I have had at least one rebuilt alt that would test fine on the store machine, but when bolted in the car would fail. I found if I loosened on of the mounting bolts the case would relax and it would start working. I got a new one I had to deliberately sabotage, the "new" unit to get it replaced.
 
Battery charges fully. Pretty much have it charged completely before any testing. I'll try your bolt loosening trick Wes. It might be crazy enough to work.
 
fingers crossed but not much faith, the other was an import car with many more bolts on the brackets
 
Do you have voltage at all 3 terminals? Typically, there is a "resistor" in the form of a light bulb in the dash, but the dash is notorious for bad bulb connections. I can't remember what happens if that connection is gone, but on some models it would just fail to ever realize the engine is running. I think there is some variation in these setups.

1779905275516.png
 
That diagram should make it charge, but some of the lesser voltage regulators could have small draw when the truck is off. terminal 1 doesn't require any input to have a good charging system.
 
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