3G Alternator Question

Kizer

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Hello All,

My 2nd replacement alternator (in two months) is "pushing" 12.4V after start up.
After I reach 3000 (or so) RPM it charges at 14.2V until I shut the engine down.
Upon start up it's back to 12.4V ... etc.

What causes this problem?

I'd like to understand the issue before I go back to NAPA.

Thank you in advance,
Kizer
 

The_Josh_Bear

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My only thought is that the alt isn't seeing the load properly. Which would mean the sense wire isn't in the right spot or otherwise the 3G is wired up wrong... I'm no electrical guru though. Maybe a loose connection even. Here's a good diagram of the conversion if you aren't sure already:

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A good 3G setup will charge correctly(14.2ish) from idle to WOT right out of the gate. I'd know, I have one! :)
 

Kizer

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Update: The second failed alt. was returned to NAPA. The one that they offered for replacement tested bad too!!
That's three straight! What are the odds ..??
Anyway #4 was (is SO FAR) a winner.

What (who) are y'all using for replacement alternators?
 

chillman88

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Apparently not

Need
Another
Part
Again

I've used Advance Auto when I need something quick. Always be really nice to them and they can test it before you leave ;)
 

chillman88

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Got it ... now.
Guess I'm a little slow after my celebration beers!

That's alright. One of the guys at work made an inside joke today and it took me entirely too long to figure it out so we're in the same boat LOL
 

aggiediesel01

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The_Josh_Bear

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What (who) are y'all using for replacement alternators?

Unfortunately NAPA has gone way downhill in the last...10 year? I dunno I'm no mechanic but they used to be the spot to go to, now they are full of bad-out-of-the-box crap like everyone else. And in a stunning turn-around, O'rielly Auto has upped their game A BUNCH in the same time frame without upping the prices significantly. Can't say much about the other parts houses.

I stopped buying them from the parts stores and use either a local shop that is willing to tell me the bearings and regulator they'll install or I rebuilt a couple using kits from these guys. Takes about an hour and I know good bearings, rectifier, and VR are inside.

This is their high current rebuild:
http://starteralternatorrebuildkits.com/product/7768/

This is their basic kit if you know your rectifier is good.
https://alternatorstarterrebuildkits.com/product/3g/

+1 on DIY rebuild! But also for starters, I've read over and over from guys that know the deal that if you can find a good repair shop for alternators/starters they last forever and actually WORK. I have nothing close to me like that I am aware of.
I bought a 3g alt from a salvage yard 10 years ago and I've rebuilt it twice because the first time I "rebuilt" it I didn't have the bearings so I only did half the job. Then the rear bearing failed me a few months ago. It was missing when I lost charge and didn't break anything somehow! Easy rebuild after that, this time with bearings!
 

chris142

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Napa's rebuilt starters and alternators are pure garbage. A guaranteed comeback. They ship the cores to china to be rebuilt. Most others ship to mexico and occasionally usa( both with global components).

At least autozone gives you a roadside guarantee of their part fails.

IMO the only thing to buy from Napa is the gold oil filters,batteries and belts.

Everything else is the same crap the other places have but with inflated prices.
 

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