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Need a GM ALTERNATOR wiring NINJA.


zeitgeist57

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Batteries - new. Advance Titaniums. 2 of them. 1000CCA

(+)to starter cable - new

Terminals - new/cleaned

Grounds - disassembled, cleaned, retightened

Starter to frame ground - added

ALternator - rebuilt, tested. 14-15v on bench

Wiring - trimmed and directly connected to battery

 

Multimeter on both - and + . . . 12.16-12.20v with car off.

Multimeter from (-)batt to - cable . . . .25-.50 milliamps (slight power draw?)

 

Engine starts, alternator spinning - no change in voltage.

Alternator excited (audible squeaking, piece of s**t) - increase of no more than .05v.

 

I can't explain why the alternator won't charge anymore than just a trickle. I've spent more than a week of evenings after work trying to isolate circuits and rewire directly to batteries to try to get the alternator to work. I was SHOCKED that Advance tested the alternator multiple times and it checks out OK.

 

Any help would be appreciated. I'm sure I did more tests, just tired/pissed/frustrated. Truck is a 1982 Chevy C20 - 6.2L diesel.

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check voltage to the back of the alt... then check the trigger wire.

 

key on engine off on the trigger wire, and dont matter on the main alt wire

 

also check the ground for the alt. and engine grounds etc.

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those old delcotrons are pretty simple the two prong plug should have a red wire and either a brown or a white wire the red wire should have 12 volts or better all the time the white or brown wire should have 12 volts or better with the ignition on. if the red wire does not have power check the fusible link down by the starter or you can cut it about 6 inches down in the harness and put a ring terminal on it and connect it right to the batt terminal on the alternator if the brown or white wire does not have power check the ignition switch

 

hth

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It's dropped since then, Vince. No more than 12.4, even with engine running. Oh, and I'm alternator #3...the one that sounded like shit did end up dying a quick death.

 

I cut the fusible links from the two-prong clip, and used both a test light and multimeter to check power to the 12v "hot" wire and the "switched" wire. All test out fine. Alternator main batt cable now splices temporarily directly onto (+)batt terminal... :(

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Can I just splice both battery and trigger wire together...temporarily...to check that voltage regulator is working properly? That SHOULD excite the alternator to generate 14v+ right away, correct?

 

two-clip wire harness IS pretty dirty, with sooty, oily schmear from being in a diesel engine bay for the last 25+ years...

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you can run a 8 gauge wire from the battery to the big post on the alt, then make a jumper wire to the trigger wire from there.. i have done this several times mounting gm alts on over various engine's! works like a charm. just dont hook to the wrong wire on the 2 wire plug..it will bang the reg right out..ask me how i know
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Sounds like the ignition switch to me. I had a friend with the same problem and that was it.

 

yes , the one channel in the switch will burn out and cause it to charge/ and not charge at times. i was thinking of this earlyer, but the damn shop phone starting ringing :D and i forgot to edit that into the my first post

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Fuck this truck. If a "jumper" wire works, I'm going to install a push-button starter, and wire everything up to switches...

 

Thanks a ton, guys. What you're saying makes sense, because my starter has been to Hite Auto Parts 2 times in the last 3 months because the starter solenoid keeps burning out...may be the ignition switch shorting out?

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Alright...

 

1) Batteries charged and tested at Advanced. 12.65V at installation.

2) New Alternator "pigtail" (terminal 1,2 connector). Rewired "1" to 12v switch as before, "2" goes to Alternator output.

3) New Battery cable tying secondary battery to primary...now, all underhood cables (hot and ground) are new.

 

Truck started right up. Multimeter reads 12.69V. I disconnect the alternator pigtail and voltage drops at the batteries. Plug it in, and it spikes for a half second to 12.75 then settles at 12.69 again. Audible noise comes from alternator when pigtail is disconnected/reconnected...clearly, the alternator is being "triggered" or "excited".

 

I leave the truck running for a half-hour. Come out, and multimeter reads 13.10 at the batteries. I open the door and turn on the headlights...voltage at batteries reads 12.80. Revving engine underhood gives off what sounds like belt squeal. Disconnect pigtail at alternator and rev engine, no noise. :eek: This is a REBUILT alternator, people. Second one since last week that's exhibiting the same symptoms (hard to spin, sounds like shit on truck, no charge). Also, Terminal 1 (pigtail to alternator #1) reads 12.74V. Terminal 2 (pigtail to alternator #2) is just above that, but under 12.80v.

 

Here's the baffling problem...I've taken this 5-mile, 2-week old alternator to Advance yesterday, and today. They test it and it reads fine. I've heard that the alternators can "test" fine but actually end up being bad on the vehicle. I complain a bit, and the guy mentions the alternator having a little friction when you spin it by hand. He offers another one to me (this would be #3) but unfortunately didn't have it in stock. I'll try another store tomorrow.

 

I'm CONVINCED that it's the alternator. At this point, the only thing I have not done is jump terminals 1 and 2 together, but I've established that the alternator is being "excited" by the new pigtail (as it was with the old one!)

 

I'm baffled at this point. Sigh... :(

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  • 3 weeks later...
Go buy an ignition switch from Autozone and I bet it will fix your problem. I couldnt reply in the other thread because it was locked up. Just make sure you have the special torx to install it. You will need to different sized sockets both available there also if you dont have them. Star sockets.
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Go buy an ignition switch from Autozone and I bet it will fix your problem. I couldnt reply in the other thread because it was locked up. Just make sure you have the special torx to install it. You will need to different sized sockets both available there also if you dont have them. Star sockets.

 

read the other thread....he fixed the issue.

 

I'm passed it. My truck is charging now, and I'm embarassed to say after 6 alternators and an entire underhood rewire what MAY have been the culprit...

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