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Bought a new battery for my 87 Elky. Drove it two miles home and the next morning even my interior/under hood lights didn't work. Took battery back and got new one. Put it in,started right up. Never moved the car. Next morning batteries dead. Never had problem before. All batteries have lasted at least 5 years. Now something is draining the battery without it running. ANY ideas? Thanks.
 

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Glove box light or under hood light illuminated with the door closed?

Bad diode in the alternator rectifier failed towards ground thus draining the battery?

Rick

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After market radio drain , that was my problem . disconnect negative battery cable & put a volt meter between the neg cable & the negative battery post , make sure key is off & remove it from ignition , if you get a reading you have a drain , if not your ok , if you do , remove fuses one by one & recheck meter , replace each fuse after checking ,this will help you find the drain . I installed a quick disconnect switch on my battery & I still open the switch when I leave the car in garage for any long period of time . The PO had wired the radio to be on all the time , I rewired the radio to the original wire (yellow) so it is only on when the key is on . Hope this helps .
 

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After market radio drain , that was my problem . disconnect negative battery cable & put a volt meter between the neg cable & the negative battery post , make sure key is off & remove it from ignition , if you get a reading you have a drain , if not your ok , if you do , remove fuses one by one & recheck meter , replace each fuse after checking ,this will help you find the drain . I installed a quick disconnect switch on my battery & I still open the switch when I leave the car in garage for any long period of time . The PO had wired the radio to be on all the time , I rewired the radio to the original wire (yellow) so it is only on when the key is on . Hope this helps .
I agree with the sources of current drain. For cars I don't use every day I've always had a disconnect switch. Likely suspects are a light some where, clock, radio, after market alarm. I do question the "voltmeter" between the battry post and the negative cable. Do you mean a multimeter set to measure current?
 

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you can also do the test Chris mentioned with a test light. light stays on till drain is stopped. i had a subwoofer amp go bad in my truck which would drain my battery enough to stop it from starting but not flat dead. i also could be wrong but pretty sure there has to be a pretty good draw to drain the battery dead overnight. would have to be something bigger than a glovebox light being left on.
 

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need some help, I have G body el camino. battery drains over nite. I disconnected both battery terminals an check the fuse box. with a fuse pen, an I still have power . If anyone have any idea what hell is going on plz help. car might be possess lol...
 

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What you have going on is a condition called parasitic drain. A normal drain from the memory of a radio shouldn't kill a battery overnight, in fact not over a bunch of overnights. There is a circuit staying active draining the battery down. Often it is a stuck relay. Problem is that the way to find it is time consuming. Here's how one often goes about finding the offending circuit. First, charge the battery completely. Then pull out your multimeter. I'm hoping you have one and know how to use one. If you don't have one, borrow one or get a cheapie from Harbor Freight. A cheap digital will do for this. Put it on the battery and get a reading. One at time replacing it as you go along, pull one fuse at a time. What you are looking for is which removed fuse causes a drop in the reading. The one that does is the offending circuit. Now you have go along in that circuit and see where the drain is coming from. Electrical issues are seldom easy and are the Kryptonite of many mechanics.
 
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