battery help

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Jan 12, 2007 | 04:21 PM

scbronco

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From: Dumont nj

battery help

hey guys well im having some issues with my fullsize 89 bronco. at about 3 i went to start the truck and it would crank slowly like 2 times then the battery is dead. i jumped it and its fine. parked it tried again at 5 and same thing. when the trucks running its reading 12 volts. all acc. are off is it my alternator or battery?
thanks

Jan 12, 2007 | 05:02 PM

bertha66

Lead Driver

Joined: Oct 2004

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From: Central Oregon

The old school way to check was to start the truck and oull the ground cable off the battery. If engine dies - bat alt. engine runs on - bad battery.

Jan 12, 2007 | 05:04 PM

scbronco

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From: Dumont nj

alright illl give it a shot tomorrow thanks

Jan 12, 2007 | 05:34 PM

BroncoRoadKill

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From: San Antonio, Texas

what year is your truck. Cause the only problem with doing it that way is if it has fuel injection you risk frying the comp.
If your only reading 12 volts I would be guessing that it isent reading but when the alt. is putting out alot of amps to charge or run something it isent always going to read 12.5v and up. The best way is to charge the battery over night and then put your voltmeter on it then have someyone crank it over if the volts drop down to 9v or more or the battery just wont hold a charge then its bad.

Jan 12, 2007 | 05:51 PM

adelyser

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If you jumped started it, then the alternator is at least producing enough to keep the engine running. You should typically see about 14 or 14.5 volts at the battery when running. I'd drive it to an auto parts store and have the battery checked, they can do it in car, and you'll know quickly what the problem is. They can load test the batteries and tell you exactly how good they are.

Jan 12, 2007 | 06:25 PM

Bob Ayers

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Joined: Jan 2003

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From: Durham, NC

Quote:

Originally Posted by scbronco

alright illl give it a shot tomorrow thanks

DON'T DO IT!!! Never disconnect a battery terminal with the engine running! The battery act like a filter for the alternator voltage spikes. These voltage spikes can destroy electronic components like PCM, etc. ....

Jan 12, 2007 | 06:56 PM

plowhand

Playing in the Dirt

Joined: Oct 2005

Posts: 2,302

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From: Southwest Georgia

O.K. try this, jump it off, drive to your nearest auto parts store. Have them load test the charging system and the batteries. They will do it for free, with the battery in the truck. Then you will know what is good and what is bad, and you will not fry your computer.