Riddle: When is a dead Battery not a dead Battery?

[Temjin]

anwser: When your car wont start but its still got 12V.

Alright here is the problem. When I started driving I checked the voltage on the battery, 12-13V. Then I drive around for a bit, (20 mins) Car is fine. I turn the car off. Come back 8 hours later and the car won't start. I check the batter again, 12V. For some reason I decide to charge the battery even though it says its full. I give it a full charge for about 8 hours. I put it in the car. Works fine, starts right up! Ok so now I drive the car for about 5 mins. Then I leave the car to sit for about 17 hours. I come back, car doesn't start!. I take the Battery to autozone to have them check it. They say its fine. I repeat the process above. The same thing has happened about 4 times repeatedly (I am currently charging the battery for the 5th time in about a week and a half) What do you guys think it could be. I don't want to pull the alternator with out being sure its that. I mean why does the battery kill itself over night?

[pulsar gtr]

Hi,

It sounds that the regulator inside your alternator isn't working 100%, you battery should measure about 13-14 volts when car is off and when it is running it should measure around 13-15 volts.which shows that the alternator isn't charging much, so when you drive you are using more power than what the alternator is generating.

Replace your alternator.

Also, try this, after driving the car, disconnect your battery and when ever you are ready to drive it again, connect it back again, and see if it is starts, you might have something that is draining your battery. But I am pretty sure it is your alternator.

Good luck,PULSAR GTR

[float_6969]

Ditto what pulsar said. This is a common time of the year for alternators and batteries. I personally think it has to do with the fact that batteries don't work as well in the cold (though they last longer) and so it puts a strain on the alternator. I could also be way off base here...

[Temjin]

Which Alternator do I need?

[NeedCAforS13]

email Nismo1182 (Kevin)... he had to get a new one too I believe:)

Sean

[xyster]

I'm having the same exact problem, but I had my alternator tested at Advance before I put it in, and they said it was good. I guess I'll get out the multimeter tomorrow.

[f s t caz]

Theres more to a battery than voltage. Amperage plays a big role in starting. If you have very little Cold cranking amps (nissan batteries usually have ~460CCA IIRC), like say 20, or 120, you won't have enough amperage to start the car.

[r34 gtr]

i got mine rebuilt. wasnt that expensive and it puts out about 14.5v now. starts instantly.

- tim

[Nismo1182]

Yup, I need to go to Autozone tomorrow and get the alternator part #. I lost the paper that had the info. My alternator puts out 14v daytime, 13.8-13.9 night time.

[slw240sx]

that battery is brand new, i killed 2 myself on his car, one old one i had, then another i bought, took it back and they said it was bad, only a few days old.... so then i got that battery thats currently in the car. but i think it might have to do with the alternator, its not properly grounded, also tighten the belt its loose i never had a chance to tighten it, it may be slipping causining undercharging. also im using a alterantor from a 90 240sx with some minor changes to the tensioner stuff it fits right on

[Temjin]

Tighten the belt? Why would it start messing up just now? Shouldn't it have started not charging properly earlier? Ive had the car for about a month and it only started a week and half ago

[float_6969]

Generally when you put a belt on, you have to tighten it twice. They tend to strech after you first put them on and then you retighten them and they stop. I'm going to have to do the same thing actually. Mine is sqealing some too.

[nismoplsr]

and if something was loosewith driving it the vibrations will make it even more loose.

so the belt could have been tight enough to start and gradually gotten worse untill it made a difference.

i would also check you engine grounds.

if the battery had full charge but the starter is not turning over that means it might not be getting enough power.

also, if you want to drive you car to Autozone they can do a full charging system check in you car while it is running.that will tell you if its the alt without having to take it out to get tested or replaced.

[Temjin]

Man this battery only reads 12V no matter what, even after I fully charge it. The battery also says 420 Cold Cranking Amps. Is that enough? I also tightened the belt and made sure that it was grounded. Nothing worked. Well anyways Im going out to buy an alternator tommorrow. I hope this works. Ill let you guys know. Im going to buy one for an 1990 240sx

[Temjin]

How do I properly ground the Alternator? Could someone post a picture or something? I think it looks right but I don't know. Ill get a picture on here to so you can piont out what Im doing wrong.

[iliketocrash]

you just ground the alternator to the chasis.

[Temjin]

Thats what I thought. Then what is Jon talking about it not being properly grounded?

[iliketocrash]

i'm guessing maybe the point where it's grounded could be rusted or corroded. Or maybe the wire could be cracked and brushing against something metal, thereby creating a short circuit. i dunno. i guess that question would be best answered by Jon himself.

[ca18det_boy]

The alt should use the blovk as a groundd.

[float_6969]

did you try taking it to advanced auto and having them test it? It's free...

[Temjin]

Doing that tommorrow I hope. I should have time, but something wierd...I put in a new battery (well an old one, but a friend of mines) and it worked fine. Im still gonna go get it tested though (the alternator)

[slw240sx]

that battery is under warrenty in my name its brand new, just use my name and cell number for the warrenty info.

p.s im sending the title out monday, its taking a while to get it back from the notary since i didnt diectly handle it , it got side tracked with my sister

[Temjin]

what is your last name?

[Temjin]

But what about reciepts? or that doesn't matter, oh and where did you get it?

[slw240sx]

rench, dont need a reciept just my cell# and name! should be in the puter and it came from advance auto parts on woodman drive in kettering .

[bighuyner]

You might wanna replace the battery connectors or at least clean them with a wire brush.

[Temjin]

They are clean, very shiny. Anyways I just replaced the alternator with a new one. (the 89 does not fit with out some tweaking:)) I tested the voltage across the battery and it was 13v. I was dissappointed until I remember Jon said he wasn't sure it was grounded right. So I changed that and it works fine. Now I have 14.5v. The old alternator was bad. I went and had it tested just to make sure when I picked up the new one. But hey Im back on the road again. Except for a couple of other problems, But I already have post about them:)