90 300zx battery dies out when parked for a few days!!!:(

[300zxcanyondrifter]

I have a situation with my car, I bought a battery from autozone, I had
a few days with the battery in my car until one day I was going to start my car
but it was dead, I checked the battery voltage it was less than 12v
so I returned the battery back to autozone, I got the same battery but new..
I decided too clean the battery cables, the battery was in my car for a few
days. until one day I was going to start my car and it was dead 9.1V
were available at the battery.. I just started my my car,
I left my engine idling, then turned off the engine, right after that I
checked the batterys Voltage 12.1V..
Im thinking I have a bad alternator, or a short
Idk what to do.. can someone help me??

[Mr93z32]

I would say your alternator isn't holding the charge, take it off and go test it at autozone also, would be my next step...

[aviatorwes]

Well one thing you can do is take a voltmeter and put the positive lead on the power wire from the alternator and the ground on the casing of it. since the alternator is way under the car you can just measure voltage from the battery wile the car is running. Turn on everything electric that you can and put a big load on the batt. If the voltage starts dropping then its the alternator. if it holds steady then the alternator is good. If the alternator checks good either way then your probably looking at a parasitic drain from a shorted wire or relay. Thats what its looking like to me personally.

[frag-me]

I think it's your alternator. If it was your battery you wouldn't even get it to turn. The only way it's your battery is if they batteries they are selling you are not charged at all.

[300zxcanyondrifter]

I took in my alternator too get tested in Autozone, and it Failed
the Alternator did not pass the Rectifier test, Regulator test, Diode test
Failed all tests.. the Alternator from Autozone costs way too much $163

Thanks guys for your help and your comments

[marty1mc]

Spend the money and get an OEM alternator or get a used OEM if you don't have the money.

For future reference, there is a simple test you can perform at home without pulling the alternator. Start the car with a charged battery, set the rpm's to around 1500 and measure the voltage. It should be in the 13.2 to 15v range. Next, turn on the major accessories, heater fan on high, low beams and fogs, rear defrost, etc. Again, set the idle at 1500 rpm and measure the voltage. If it is below 13.2v or above 15v, you have a bad alternator.

[Ace2cool]

Failed all tests.. the Alternator from Autozone costs way too much $163

That's actually pretty cheap for an alternator.......

[Mr93z32]

Failed all tests.. the Alternator from Autozone costs way too much $163

That's actually pretty cheap for an alternator.......

It is indeed... MIne was 200 ish

[300zxcanyondrifter]

Then I guess the alternator from Autozone is
at a decent price then compared to a oem Alternator, I heard that a Alternator
from Autozone doesn't last that long they go bad

[vg1134]

yeah-anything pretty much anything from autozone is a 6 month shelf life. why dont you take it to a rebuild shop. It might end up being cheaper and you will still retain the oem alternator.

[marty1mc]

Then I guess the alternator from Autozone is
at a decent price then compared to a oem Alternator, I heard that a Alternator
from Autozone doesn't last that long they go bad

Sometimes they are worse than just "go bad." I had one go bad with the regulator and over-voltage +18.5V. It blew out my headlamps and wiped out the air door motors. It sucked...

[nefarious300zx]

hey i just got a 90 na im fixing up and i think it drains the battery out in a few days as well but it hasnt been running much just to move it around so far im doin body work on it. anyways where/how would i test for a parasitic drain? resistance from point to point? not too sure on this one