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Old 12-02-2005, 07:54 PM
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Alternator help, prob. diagnosis

I think my alternator is dying due to being ran with a corroded and loose, positive batt wire connection for a couple days.

Here's the problem:

The volt meter drops to about 10.5 - 11 V right after I start the truck. After a couple minutes it will slowly go up to about 13.5 V (I think this is due to the electric choke shutting off on the Holley). During the day my volt meter stays at about 13.5 V, at idle or while driving. When I turn on my headlights, the volt meter drops to about 10.5 and if I keep driving with the lights on it will keep dropping to about 10 V.

Any idea's:

Diode's?
Brushes?
Regulator?

I guess I should tell you this is in my 76 K5 Blazer. The alternator has a flat plastic fan instead of the metal fan. I think it may be a late 80's Chevy truck alternator, possibly a 94 amp.

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Old 12-03-2005, 01:55 AM
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Never mind.



Well, I went to autozone and bought a new alternator and a rebuild kit and was going to take back the one I didn't use. I have a buddy that works there and he said he'd take the old alternator as a core even if it was in pieces.

So I got home tonight at 10 PM and went to pull the alternator (I figured it to be about a 1.5 - 2 hour job, tops). I put my hand on the pulley and thought about belt tension. I tryed to turn the pulley by hand and guess what, it turned quite easily.

So, to sum it up, I tightened the belt, started the truck and let it run in the drive-way for about 5 minutes with the air and headlights on high and it stayed above 13 V the whole time.

I hate forgetting to check the simple things first.
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Old 12-03-2005, 05:30 AM
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Quote:
Originally Posted by 70bird

I put my hand on the pulley and thought about belt tension.

I tryed to turn the pulley by hand and guess what, it turned quite easily.

So, to sum it up, I tightened the belt, started the truck and let it run in the drive-way for about 5 minutes with the air and headlights on high and it stayed above 13 V the whole time.

I hate forgetting to check the simple things first.
But at least you did and it saved you money to be spent elsewheres on it...
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Old 12-03-2005, 09:23 AM
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...and I bet that you'll never forget to check for a loose belt in the future. Congrats on you discovery and return of funds!
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Old 12-03-2005, 01:51 PM
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Doc here,

Easy is always cheap!

Now invest a little of what was saved in a new belt and you'll be gold!

Thanks for the reply!

Doc
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Old 12-03-2005, 08:20 PM
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I put new belts on in august but I never rechecked the tension after I drove it a couple hundred miles.

I heard once that you should recheck belt tension on V-belts because they stretch a little bit after the initial install.
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Old 12-04-2005, 08:07 PM
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Never hurts to press on them occasionally to see if they've loosened up on you, while the engine is not running, of course!!! LOL!
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