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Old 06-15-2010, 03:34 PM   #1
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Exclamation Jeep Wont start. battery or alternator?

So this morning, i started my jeep several times without a problem. Then suddenly at the store, I tried to start it up, and nothing happened. I tried a couple times and there were some weird humming and buzzing noises coming from under the hood. The gauges started flicking, so I got someone to jump it. That worked fine, and then after driving it 2 minutes, the CHECK GAUGES light on the dash comes on. I have my wrangler idling in the driveway, and i think it is the alternator, because it will not hold a charge...

PLEASE HELP!!

thanks,

Andy

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Old 06-15-2010, 03:37 PM   #2
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and also, when it is idling, the battery gauge is just barely flicking at half

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Old 06-15-2010, 03:39 PM   #3
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Check the battery cables first, clean/replace them if corroded at all
Have the Alternator checked and if OK then change the battery
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Old 06-15-2010, 03:44 PM   #4
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If its idling outside, its the battery.

Alternator keeps it running...Battery starts it.

Always a good idea to check cables as well (any corrosion is bad)
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Old 06-15-2010, 03:44 PM   #5
Knows a couple things...

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I would first remove both battery connectors from the battery, clean them thoroughly with a wire brush and then reinstall them and tighten the mounting bolt securely. A loose/dirty/corroded battery connection is the most common source of the type problem you're having.

Never is the alternator a reason why an engine won't start unless the battery went dead from a dead alternator. In the TJ's case, that's unlikely since the TJ's alternator is known to be very (!) reliable.

If cleaning the battery connections (both the battery posts and connectors) with a wire brush doesn't help, odds are the battery is dead. Charge it overnight as a few minutes or hours on the charger is never enough when it is dead. If that doesn't do it, remove the battery and have it "load tested" by your local auto parts store to determine its health. The battery may either be dead or simply in need of a good thorough overnight charge.
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Old 06-15-2010, 10:07 PM   #6
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I just had this happen recently also. It was a loose battery cable to the relay box. Not real loose just enough to break contact on bump etc. So clean and retighten them and that should do it.
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Old 06-16-2010, 12:49 AM   #7
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i had the same symptoms and ended up replacing the battery about a week ago and no problems since. now that i said something its not gonna start tomorrow
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Old 06-16-2010, 09:38 AM   #8
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I have this problem periodically. i just pull the cables off and clean the posts real well until they shine.
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Old 06-16-2010, 09:50 AM   #9
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yes, clean and check everything, mine was loose on the starter side of the + cable with the same symptoms.

two things on your battery, have it LOAD TESTED. Shops will do it free... If its more than five years old or has any swelling on the short sides, replace it.

And remember guys, shiny is bad... you want to ruff it up really good with a wire brush or sandpaper. Then the two mash together as one. Its the same principle as the cross-hatch pattern in your cylinders when re-building. With being rough, you get the most surface to surface contact. With being shiny, there are only a few parts actually touching each other between the connector and the post.
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Old 06-16-2010, 12:05 PM   #10
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Yeah, it was the cables. I'm just going to replace them since they are so loose. The guy who had it before me tried to shimmy a piece of metal it tighten it up, so that was the culprit. The cables are also pretty eroded as well. thanks for the help!
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Old 06-16-2010, 12:18 PM   #11
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cool find. When those cables get all nasty, if your going to pitch them anyways... cut the insulation back about an inch or so from the connector and peel it off. A lot of times you'll see just how green and cooroded the copper is in there.

Even with putting new cables on, clean up the terminals with a wire brush before you put the new ones on. And if the new connectors are all smooth on the inside, ruff them up a bit before installing.

If you plan to clean the battery while working on it, use a little baking soda and water with an old toothbrush that you can throw away when your done. If it bubbles and foams, it is killing the acid residue. Rinse it good and it will look new again

If any of you guys have a volt meter handy, here is a little test about just how dirty your battery really is. You'll be surprised how little crud can arc electricity and short your battery out. With the Jeep off, Touch the + from the volt meter to the + of the battery. Then touch the - to the - side of your battery. You should see your 11-12.5v reading. Second, keep the + side on the battery terminal and touch the - side to the plastic in the center of the top of the battery. If you see ANY voltage, it is arcing accross the top. After cleaning it, there will not be any voltage accross the plastic. We all know plastic cannot conduct electricity, but the thin layer of crud will!
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Old 06-16-2010, 12:23 PM   #12
Knows a couple things...

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Quote:
Originally Posted by VVCG33 View Post
Yeah, it was the cables. I'm just going to replace them since they are so loose. The guy who had it before me tried to shimmy a piece of metal it tighten it up, so that was the culprit. The cables are also pretty eroded as well. thanks for the help!
You can get those connectors tight again by using something like a Dremel wheel to shave lead away inside the gap that the connector's tightening bolt squeezes together. I shave about 1/8" off per side. That will allow the bolt to squeeze the connector closer together so it is tight again. I've done this to both my TJ and my son's Grand Cherokee to get the connectors tight again.
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Old 06-16-2010, 12:34 PM   #13
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Quote:
Originally Posted by Jerry Bransford View Post
You can get those connectors tight again by using something like a Dremel wheel to shave lead away inside the gap that the connector's tightening bolt squeezes together. I shave about 1/8" off per side. That will allow the bolt to squeeze the connector closer together so it is tight again. I've done this to both my TJ and my son's Grand Cherokee to get the connectors tight again.
thats a nice little trick jerry ill have to remember that one.
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Old 06-16-2010, 01:01 PM   #14
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Seven - that's a good way to tell when your battery needs a bath. LOL

Speaking of unusual voltages - clip your (+) voltmeter lead on ground. Dip the (-) lead in the radiator water - don't touch the metal. Use a low voltage scale - .5 volts is normal, and if I remember right it, it goes up by about .75 each year the coolant is in it. That's electrolysis - eating your engine from the inside.

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