Car won't start

Ok, I can't get my car to start. This is the second time it's happened in a couple weeks. I turn the key and it tries to start but just turns over maybe once or not at all really slowly. No clicks or anything. I'm guessing my battery went dead but why would it? I didn't leave anything on. This time I didn't even have my alarm on so I dont know what could have drained it. So then I'm thinking maybe my alternator just isn't charging it when I'm driving. Anyway, my question is can I test the battery votage with a multimeter while the battery cables are attached or do I have to disconect them both? I don't want to disconnect them because it resets my trims and then my cars drives like crap for a while. Also, is testing the alternator easy or should I go to a shop to do this all? I know pep boys, etc test your electrical problems for free so I could do that too. Just dont know which one to do.

Oh, and my headlights turn on (maybe a little dim though) and all other lights work so it's not completely dead.

Have you gotten it started and running with a jump or a quick battery charge? If so, and it runs fine after starting up, then it isn't your alternator.

Try to check the car throroughly for any light that could remain on because of a broken plastic switch or an aftermarket L.E.D--for example, when I leave my sub amp switch on, the L.E.D on my amp drains the battery if I don't drive the car for a few days.

Sounds like your battery itself to me. I'm no electrical expert, so I don't know the answer to your multimeter problem. I don't know why your "trims" being reset would be such a big deal...what are you tuning with?

The only stuff I have on my car is in my sig. I don't have any lights or anything. I'll check tonight if something is on though. So if I jump start it and it runs then it's not the alternator? I thought it might not be charging it when I'm driving. I leave my car for like a week at a time without driving it. Could that do it?

The alternator charges the battery while you're driving. While you're driving, your car is running a few applications that slowly draw power. Eventually the car would die with a busty alternator. If the alternator is working properly, that couldn't happen-- more than enough juice would be supplied to the battery.

Leaving the car for awhile without starting it slowly drains the battery, but no so quickly that there should be a problem.

The ECU trims shouldn't readjust unless the battery has been pulled for a few minutes. The ECU still has residual power.

This may not be right... but if you're trying to test the battery with a multimeter while it's still attached, I don' think there would be a problem. The worst I can think of happening is frying the fuse on your multimeter. Don't follow my logic here, even I don't trust it. That's just my best guess.

Why take the chance, just get the battery off and test it.

My bet is that your battery is dead.

Joe Mathews, it's not the LED light that's draining, it's the amp itself. The draw off a basic LED is so small that it should take something like 6months (probably longer) for it to drain. Think about it, if your LED light is on, then your amp is on too. Even if there's no music, that's still a major draw from the amp.

I suspect a bad battery, bad ground or power cables, or bad altinator. You can have a battery that seems OK but if it has been abused or is older, usually the lead plates go. Altinators can seem OK too but might have a "dead spot" where if you shut off the car and it hits this spot, the alt. will gound out and discharge the battery. The cables are selfexpanatory. Your car might seem OK but because one or both could be bad, the battery doesn't get charged right.

Ok, so I took it to a shop and ended up just paying them to fix it--$650! They rebuilt the alternator and put in a new battery. Battery was apparently at 9.4 volts and the alternator was at 61 amps and 12.96 volts. I figure I could've done it myself for around $200 but oh well. Thanks for the help though guys.

Btw, I just drove an hour to school, got out of the car and saw that my e-brake had been up the whole time. Crap! It was only a couple clicks though so I'm hoping it's fine. lol