So I went travelling and didn't use my car for two weeks. When I left the battery was fully charged and ready to go.

When I came back, it had drained completely. Not even enough juice to activate the automatic door locks. Apart from looking like a tool, having to break into my own car just to get inside, I noticed again that when I replaced it with another freshly-charged battery, let it sit for a couple of days, it really struggled to get the engine cranked over.

But it did, and after I drove it and the alternator had a chance to do its job, it was fine again.

The battery is slowly draining itself while in the garage, and short of disconnecting it each time (which is impractical because I have a keyless entry system that requires the battery to be hooked up and if I disconnect, then I can't get back into my car), I don't know what to do.

Anyone have any ideas what could be causing it?

You obviously have a draw of some sort, now you have to determine what is causing the draw.

Yeah, but I have no idea how to test for a draw- something to do with the ECU maybe? (I guess it could be anything in the entire electrical system, no?)

Is there anything I can do with the fusebox to determine where the draw is coming from?

Take a testlight, attach one end to the negative battery cable. Probe the negative battery post with the other end. Carefuly remove the cable, make sure the teslight is in contact with the post and cable at all times. Then have a helper start to pull all the fuses. The light will go out when a circut that has a draw, gets cut off from removing the fuse. There will be more than one circut, some of the accesories drwa power all the time.

Chris,

I'll try that- thanks!

Well, Tried the tester light, pulled out all of the fuses, one by one, from the fuse boxes in the engine compartment (2 boxes) and from under the driver's steering column (1 box), but the light never went out.

Tried each and every fuse and FINALLY pulled that tricky alternator fuse and that extinguished the light!

NOW, This is the third alternator I've had in the last two months, and I'm gonna' rip into the dude who installed it for me something fierce tomorrow!

Thanks for the advice Chris!

Sounds like you have a bit of a wiring problem. Three alternators in two months sounds a little fishy.

What wiring could there be though? I think it's a pretty straight-forward connection between the alt. and the fuse/battery.

I read an article online from http://www.misterfixit.com/baddiode.htm that explains how this 'battery drain' problem occurs. I doubt it would be caused by a wiring problem, unless it was that the guy who did the installation who wired it improperly (the website suggests that this particular mechanic had 'clocked the connectors', and changed the alternator connections from side-mounted to rear mounted, and thus had blown a diode inside of the alternator.

Thus, the alt. would pass the voltage test, but fail the current load test. I think the problem is with either the alternator or (likely) the installer. I might have my next alternator installed by someone else. It's just a Royal f*#$&%g piss-off.

I would suspect the rectifying diodes too.

what they do is that they are one directional valves. the electricity could go from alt to battery but not back. that is why that circuit is always alive. it controlls itself with the car off.

Once the alt is off the car or atleast the cable is off you could test it with a meter and see.

it should conduct in one direction but not the other. I think if you connect the positive end(usually red) of your meter in DIODE or RESISTANCE(diode is a little triangle with a bar at the end) and the negative to where the thick cable from the battery is connected you should see conductivity but not the otherway around.


The thick cable's end is the positive output of the alternator. the Negative is the body, and the two other ones: one is for field excitation and and the other is for battery warning light!(DSM's battery warning light is THE MOST stupid thing ever)