I have an 87 z28 305, with the battery hooked up and the car completely off (i.e. key out and in off position) after about a week of no use my battery is completely dead. Took the battery to auto store, they tested, sure enough its so dead it cant be charged. Battery was 2 weeks old, also new alternator is 2 weeks old. Where can i start in trying to figure out what is destroying my battery???

Only thing I can really think of, is cold weather. Do you live in the north?

Bad battery cables will also do that. Check out your cables for corrosion, and try replacing them if they're corroded at all, and see if it helps any.

cables are good, not new but decent. i live in texas cant be cold weather doing it, hahaha

I had a similar problem. Sometimes it would last a day sometimes a couple days.
Check the bat cables--make sure they are clean where ever they connect.(bat terminals & ground, & starter wires, alt connections)

My case turned out to be a broken solenoid connection & alternator connection >>What the starter had to do with it IDK.?.<<
but a new starter & rebuilt alternator I've had no issues.

sounds like you have a small draw coming from a circuit, you are going to need a amp meter. I don't remember all the steps, but do a search on battery drain and you should find your answer.

I found the steps to find a parasitic battery drain, i'll have to try to find the problem when i can get my hands on an ammeter. I'll post what i find out.

It sounds weird, but it's something easy to check...

When it's dead quiet outside, open the hatch, and place your ear on the hump, and listen for the fuel pump whine - if it's running with the key out, then it's your Oil Pressure Sending Unit - they can go bad in such a way as to make the fuel pump run all the time, regardless of the key - and the fp can drain the battery in about 4 days.

Thats interesting, I will definitely have to check that today as well.

Alright, hooked my amp meter up to the battery cable and battery terminal. I'm getting 2.25 max, doesn't seem like it would be enough to cause a battery to be completely dead in a week of no use. But I could be wrong, any ideas?