problem with battery?

[moondoggy1302]

I own a 70 chevelle malibu, it has a 350 in it and a after market stero system. So heres my problem. Something is sucking out the power while the car is off. thought it might be the amp cord so i undid it but still dies while just sitting there...off. I have no idea any sugestions? im gonna check all the fuses seeing as i havent yet and have only owned the car for about a week.

[highlandlake]

Welcome to the site.
Carefully remove all the glass fuses in the fuse panel. Charge the battery first. If the battery is still good in the morning, or however long it's taking the charge to go flat, then you know the culprit is one of the fused circuits.
If the battery is flat after pulling all the fuses, then focus on the engine compartment direct circuits. These would be the starter, voltage regulator, distributor, and some others.
You can attach a test light or meter from the negative battery cable to the battery post and experiment with the fused circuits until you find the item that is causing the drain. Don't overlook the door light switches even if the dome light goes off when the door is closed.
I guess I'll also add that you must have a basic understanding of circuitry before you start working on this. Otherwise it's possible to damage acccessories or create power drains where none existed before.
You probably have this skill, but I thought I'd mention that. There are many good electrical troubleshooting articles posted in these forums if you care to do some research.
I'm betting your problem is a simple one, and that you can locate it fairly quickly. Good luck and please post back with your results.

[SpinnerCee]

Make sure that the aftermarket sound system isn't killing the Batt -- Radio station preset memory requires some power to maintain, but it shouldn't kill the batt overnight -- some people mis-wire amps to an always-on (like directly to the battery) circuit to avoid the pops during starting and the amp(s) can kill the batt overnight, but they should really be wired to a circuit that's hot during run (key ON) and start.

The HEI distributor (if ya got one) is also another issue -- it should also be wired to a circuit that's hot in run and start, but many wire it to a constant 12v circuit that will work, but drain the batt excessively, and possibly damage HEI itself.

* On my '70, there are two accessory (ACC) tabs in the fuseblock under the dash -- one is hot in run and start, and the other is hot in run, but not in start (while cranking) -- connecting the HEI to it by mistake creates a really funny no-start condition where the engine will not start while cranking, but will sputter and try to start after releasing the key... A voltmeter is invaluable here.

Often a battery that cannot maintain a charge is just dead -- replacing it with one of known quality will probably solve many of your intermittent electrical issues.