I NEED YOUR INPUT/HELP! PLEASE, Can an alternator drain a battery with car off? Options

[Random_Stranger]

Ok so I have this issue where my car battery is suddenly being drained by something. I was just wondering what first things to look at. Also what I find strange is that it didn't want to start last night (I witnessed a hit and run across the street, thought the guy was gonna stop but when he took off, I was going to jump in my car and get his license plate number, but my car didn't start). So I busted out the voltmeter and seen it was like at 9.38v. I set my alarm and went inside and later that night, I hear my alarm chirping in a way I never heard before. Then it got louder, and louder and then just went off making it's normal sound if someone attempted to break in. So I go out there and disarm it. Noticed my lights were dim and checked the reading again. It was 7.38v. I left the voltmeter connected to it and sat in the car wondering what it could be. I went back and noticed it climbed up a bit to 7.44v. I let it sit there and watched and it climbed up to 7.48v before I just disconnected it.

Is that normal for a voltmeter to do that? You think it might be my car alarm? I have an optima battery which is like 3 years old. Not sure what the life expectancy is on those or if maybe it is in fact something draining power.

This post has been edited by Random_Stranger: Jan 9, 2012 - 4:39 PM

[Smiles98]

Mine does the same thing, for me its to cold for the battery to maintain a good charge.

Ok the first thing to do is to run the car get the battery back to 12.2 (ish) volts turn off the car and disconnect the positive post on the battery connect a test light to the positive post on the battery and the positive cable. if your cable is grounding out than the light will turn on. also try on subwoofer power wires. (allow 2 min for light to turn off for normal systems to shutdown.)

If its not the wires, than keep the cables hooked up and turn the car to acc mode, then turn it back off and pull the key and close the door(s) the light will turn on in the test light.
wait 2 min for light to turn off if it dosn't than pull the power to the alternator (the alternator has diodes that if diffective will pull power from the battery) wait another 2 min for light to turn off. if light stays on replug alternator.
Now start pulling fuses. if the light shuts off abruptly when you pull a fuse than its in that part of the system that the power is being drawn. not the best way to find the problem but very effective.

my test light faded slowly without pulling any fuses so i came to the conclusion that im not really losing power through the system but i might be wrong.

alternator would be the first thing i would check and good luck