loosing battery power
Corvette Enthusiast
Joined: Oct 2007
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From: So. Cal.
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Team Owner
Joined: Dec 1999
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From: Lacey WA RVN 68-69
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With the instrument cluster out, there could be an open circuit somewhere.
But first, how long does the battery last? I'm assuming that at some point the battery won't turn the engine over, right? Is the battery fully charged? A full charge should show 12.8v using a digital volt meter.
With the engine running, what is the battery voltage? What is the voltage at the large terminal at the back of the alternator? A good alternator should be putting out anywhere from 13.6v to 14.3v depending on the battery's state of charge.
Thread Starter
Instructor
Joined: Jun 2006
Posts: 156
Likes: 0
From: homestead florida
loosing power
Im not sure what the output is Im going to check tommarow ,the battery was new and fully charged now it wont turn the engine Ive been disconnecting it every day to prevent this but no sucess Ive had the alternator tested by a shop here in homestead and he said it had no problems so now I turn the infinite wisdom of the forum, serously Ineed some direction before the other half deems its a P.O.S. and wants me to get rid of it
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
If your new battery is discharged and won't crank the engine, charge it up with a battery charger. Do not let it sit discharged. Your battery may be being discharged by high leakage current (current flowing with the ignition off). Unplug the courtesy light fuse and connect the positive cable to the battery and connect your multimeter set to amps between the neg cable and the neg battery post. GM says leakage current should not exceed 50 milliamps. My 87 draws 27 ma and I have no battery problems. Remove the fuses one at a time and watch the ammeter. A large drop in current will tell you what circuit to further investigate. At night connect the battery cables and see if the vanity mirror lights are on, underhood lights are on, door map lights are on, center console light is on. Don't leave your keys in the ignition because this keeps the anti theft circuit on. Do you have a radar detector, CB, GPS, aftermarket alarm, aftermarket radio or audio amplifier? Check em.
Burning Brakes
Joined: Oct 2009
Posts: 773
Likes: 2
From: Minneapolis MN
If your new battery is discharged and won't crank the engine, charge it up with a battery charger. Do not let it sit discharged. Your battery may be being discharged by high leakage current (current flowing with the ignition off). Unplug the courtesy light fuse and connect the positive cable to the battery and connect your multimeter set to amps between the neg cable and the neg battery post. GM says leakage current should not exceed 50 milliamps. My 87 draws 27 ma and I have no battery problems. Remove the fuses one at a time and watch the ammeter. A large drop in current will tell you what circuit to further investigate. At night connect the battery cables and see if the vanity mirror lights are on, underhood lights are on, door map lights are on, center console light is on. Don't leave your keys in the ignition because this keeps the anti theft circuit on. Do you have a radar detector, CB, GPS, aftermarket alarm, aftermarket radio or audio amplifier? Check em.
Keep in mind that just because the alternator "tested" good doesn't mean that its not the source of your "draw".Is the interior lights or anything staying on after car is shut down & key is in your pocket?What year is your car?I've seen starters & alternators draining batteries.Disconnect alternator at both connections & see if battery still goes dead.If it does reconnect it & disconnect starter wires & see if battery goes dead-both these tests are easy if you do not understand above testing method.Post results
