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16 to 17 volts on battery post - alternator?

Old 11-06-2009, 08:11 PM
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16 to 17 volts on battery post - alternator?

Can my alternator be bad? Im thinking can it be that I did something wrong when I rebuilt the starter.

110K miles 94 V6 4X4

The battery light and brake light come on intermittenly while driving. Truck runs fine though. Next morning my new battery only 2 volts -then I have to recharge it.

Brand new battery with the truck running, I get 16.58 volts to 17 (no kidding) when I put voltmeter on the battery. I read here it should only be in the 14V range. When I turn off the truck, I get 12.58 volts. In 20 minutes, the voltage drops to 12.0. If I let the truck sit on the driveway over night, the battery gets drained to 2 volts.

Some one mentioned rebuild alternator with 90amp stator kit. Where can I find a stator kit, none on eBay?

Thanks for the advise fellas.

Last edited by arielb1; 11-06-2009 at 08:19 PM.
Old 11-06-2009, 08:53 PM
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I would unhook batt. charge it and see if it holds a charge unhooked from truck. (16+ volts is hard on a batt.) Then the voltage regulator does not seem to be doing it's job, should be in the 14.6 range. If it (Voltage Regulator) is built into the alt.??? take the alt. in to be tested.
Old 11-06-2009, 08:59 PM
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Originally Posted by Donsway
I would unhook batt. charge it and see if it holds a charge unhooked from truck. (16+ volts is hard on a batt.) Then the voltage regulator does not seem to be doing it's job, should be in the 14.6 range. If it (Voltage Regulator) is built into the alt.??? take the alt. in to be tested.
yeah, the battery does hold the charge unhooked from the truck. I had it sitting on the counter for days and did not lose one volt.

other thoughts? many thanks
Old 11-06-2009, 09:13 PM
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The V/R is in the alt. pull the alt. and have it tested.

If you are lucky everything wrong is in the alt. May have a short in/around the starter but check that alt. out first. Auto Zone or the like will test it for free.
Old 11-06-2009, 09:20 PM
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Last edited by Donsway; 11-06-2009 at 09:21 PM.
Old 11-07-2009, 12:41 AM
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You have a power draw somewhere. Also sounds like the output regulator is bad on you alternator.

You can check for power draw by unhooking the HOT (+) side of the battery & connecting a volt/ohm meter between the battery & terminal connector. Make sure EVERYTHING is off. This will show how many amps/milliamps you have drawing. Start pulling fuses until the current draw drops. Your culprit will be on that circuit.
Old 11-07-2009, 08:10 AM
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I've got a gut feeling my alternator is bad and I might as well replace since it is original.

TNRabbit, thank you so much for the electrical lesson. Im going to try this today just so I can learn.

GNarly, I dont know what IC Regulator is, but it appears to be part of the alternator. Im hoping by replacing alternator or rebuilding it, the problem will be resolved.

Many thanks
Old 11-07-2009, 08:58 AM
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A very easy way to check amp draw is with a meter that has a amp clamp. You can see how many amps are being pulled from any wire you can get to without unhooking it. Was able to find a A/C compressor clutch on one car that was not turning off this way. Great way to see how many amps are being pulled from the alt. aswell. I am a bass head with a 200 amp alt. two Yellow Tops, and soon to install a 2nd 200 amp alt. With the amp clamp I can see all that power flowing to the amplifiers.

http://www.google.com/products?hl=en...-8&sa=N&tab=wf
Old 11-08-2009, 01:02 PM
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Well, just a follow up so I do not leave future members hanging. The drama is over. Problem solved.

I replaced the alternator with a rebuilt one. There is Pacifice Exchange Rebuilders in Los Angeles, Canoga Park area. They rebuild all kinds of parts from axels, power steering, alternators etc. I got one for $62 with 1 year warantee. AutoZone charges $130 for same rebuilt amp. I had the owner show me and verified my alternator was broken.

Now when the car is running and I place the voltmeter on the battery, I get 13.9 Volts instead of 16. I later learned 16 volts is very bad for the battery. 14Volts is normal range that I have read on this forum. The truck started right up the next morning, and no more battery or brake lights on my console.

The alternator was easy to remove for the most part. 10, 12 and 14mm sockets, but a 10 mm ratcheting wrench was helpful with the electrical ground connector. The other electrical connector is just a pinch and pull connector. However, it was difficult to get loose since my hands are not very strong. Two bolts (top and bottom) are needed to be removed to get the alternator out. Once it was loose, drop it to the bottom of the truck to get out. I did not remove the airbox, although it could have been easier. I did have to remove the dipstick. This was an easy task..just make sure you apply proper pressure to the belt before securing.

Thanks for the electrical lesson. I always wondered what the heck that amp clamp was for. On the google link, which should I get. Im going to buy one just to learn how to use it. Any suggestions which one I should get? Please provide link and I will buy it - ebay, amazone ...etc...many thanks for the lesson.

Many thanks for the help everyone...
Old 11-08-2009, 01:51 PM
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If the alternator is shorted out it will have a parasitic draw thus bad alt.... check for a draw...
Old 11-08-2009, 02:49 PM
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Thumbs up

This is a new model of what I have. Mine has made it 5 years and still going strong. I am a handyman so use it on just about anything you can. Fluke is a very good meter but has a price to match.

http://www.sears.com/shc/s/p_10153_1...26+Meters#desc


By the way, with a amp clamp all you have to do is put the wire you want to test in the clamp, and it shows how many amps are being pulled through that wire.

Glad you are back up and running!!!!!
Old 11-08-2009, 08:01 PM
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NIce amp clamp. I was looking through eBay for an amp clamp. Thanks for the lead. I will pick one up this week. For the meanwhile, I will look around how to use it. lol, I will hook up to my alternator to see whats normal.

thanks...cheers.
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