Replace/repair alternator?

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Stan
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Replace/repair alternator?

Post by Stan » Wed Nov 21, 2012 2:09 pm

As close as i can tell [ voltmeter connected to the alternator output/batt terminal ] my alternator is only putting out 12.5 - 13 volts. The same voltmeter shows 12v on the battery so i'm assuming it's reading correctly.
Since i think the alt is supposed to put out 14 to 14.5 v i'm wondering if i need to replace the alt or just do some further testing.
What's the proper way to test it? I didn't disconnect any wiring when i did the test ; just hooked the voltmeter to the output terminal.
Stan
Oh the battery is fully charged - and i also tried the test with headlights on and off - same 12.5 volt reading.
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maui
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Post by maui » Wed Nov 21, 2012 2:45 pm

Voltmeter connected to the battery. Check without running first and then running. Should read between 13.8v and 14.5v when running. Typically about 12v when not running.

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Stan
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Post by Stan » Wed Nov 21, 2012 2:56 pm

That's how i initially tested it - voltmeter to battery - running and not running - read 12.5 v and 12 v respectively.
stan
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Post by Scodge » Wed Nov 21, 2012 3:01 pm

The problem may net be the Alternator. Depends on your setup. Do you have an external or internal regulator? Check the connection between the battery and the charging wire, and check the wire itself. They wire may be loose or corroded, or the regulator may be bad. You can also pull the alternator and take it to a good parts store where they can test it. call them first to make sure they have a test rig.

Ideally, you want 14.7 volts with the engine running an no accessories on. Try gunning the engine a bit and see if the voltage rises. Externally regulated alternators don't always achieve full voltage at idle.
Scott
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Stan
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Post by Stan » Wed Nov 21, 2012 4:01 pm

stock type setup - external regulator - 75A alt - new Painless harness. I'll check for loose wires first. If i find nothing it sounds like removing it and taking it to be tested is the best idea.
thanx
Stan
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Post by Scodge » Wed Nov 21, 2012 5:56 pm

Good time to convert to a 3g or Delco alternator with internal regulator. Buy it at Napa if you can, they have a lifetime warranty, if I remember right. The conversion is pretty easy, and well worth it.
Scott
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Post by Viperwolf1 » Wed Nov 21, 2012 6:08 pm

I want a second opinion on voltage readings from a different voltmeter. Everything looks normal with the exception that the voltage readings are all about 1 volt low. You should notice cranking problems with the battery at just 12V.
Phil

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Stan
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Post by Stan » Wed Nov 21, 2012 6:13 pm

good idea - i think i can locate a couple more voltmeters - take an average -
It was cranking slower and slower everytime i started it this week.{6-8 times} so i hooked the trickle charger up and gave the battery a full charge - cranks over pretty good when charged.
Stan
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Post by 69brightbluebronco » Thu Nov 22, 2012 12:42 pm

3G alternator is a really easy to swap in. but since doing that i think i need to get a serpentine belt setup now and then, the V belt doesnt give enough tension and it squeels under high load like jump starting or start-ups on cold days.
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Post by BroncoDave » Thu Nov 22, 2012 9:37 pm

69brightbluebronco wrote:3G alternator is a really easy to swap in. but since doing that i think i need to get a serpentine belt setup now and then, the V belt doesnt give enough tension and it squeels under high load like jump starting or start-ups on cold days.
I had fits with the squealing pulley when I did my 3G conversion. The aluminum one, a pretty chrome plated one, and a gold anodized looking one all squealed. Finally I installed a old stamped steel pulley and no more problems. Maybe a quick chirp on startup if I have used the battery hard but nothing more than a chirp.
David V.V.
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70 Bronco

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Stan
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Post by Stan » Mon Nov 26, 2012 5:32 pm

I removed the alternator and had it tested -and it was "just fine". So i bought a new voltage regulator , installed it and double checked all the wiring and grounds . Now according to my voltmeter with the motor idling the alternator is putting out a strong 13.5volts vs the previous weak 12.5v. so it was either a bad reg or a bad ground. Either way i think it's fixed. I hope. :?
Stan
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Homer - " Facts are meaningless . You could use facts to prove anything that's even remotely true."

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