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Discussion Starter #1
My electrical system stopped charging the other day. Background on my setup:
CS130 alternator (with american autowire conversion harnesses)
red top Optima battery
stock everything else.

When the car is running it shows about 11 volts (on volt gauge and on engine computer using a scanner). Initially I checked the main post on the alternator and it was reading 7 volts (while running) and the excitation wire is showing 11.5 volts. The battery was showing 11 volts running and about 11.5 not running. My initial thoughts were that the alternator was bad. I took it to the local parts store and they checked it, said it was good. THe alternator was old, but I changed it for a new one anyways.

I installed the new alternator and had the same results except that the main post on back of alternator was now 4 volts. I then took the battery to the local parts store and they could not check it, but since it was still in the 3 year replacement period they exchanged it for a new one. Put new battery in and had 12.5 v static and 11.9 to the excitation wire and the main system was 11 volts while running.

I checked all of the wiring (and grounds) and even changed both battery cables out (each cable had one of their ends seperating from preformed connections). Still after changing them out, still have the same results.

I suspect that maybe the "new" alterantor is bad but I am still confused. The car has been running great and I haven't changed anything out lately, it just started doing it. If anyone might have anymore suggestions, please let me know.
 

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Is the alt case and negative post on the battery at the same potential? Any voltage between them? Should not be any voltage.

Remove the BAT red wire and measure the stud voltage referenced to ground/case.
Is the alt case hot, meaning alt is converting mechanical energy to electrical energy?
 

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Ditto
 

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Discussion Starter #4
Found problem!

Finally figured out that a section of the alternator wiring harness (about 6 inches away from the main post of alternator) was corroded and that was the culprit.
 

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Glad you found it...thanks for posting back.
 
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