Alternator/battery ?s

[rancid240]

I changed out a battery recently that was dead (around 4-5 years old, so I didnt think anything of it) with a fresh one from Pep Boys. I moved the car from parking space to parking space about twice in a two week period, then checked the car and battery was dead again at the end of that period. So I got it charged at pep boys and read my voltage at idle, which was only 13v. So I removed the alternator and had it tested, and it was bad. Replaced that and thats where I am today. (Just an FYI its much easier to remove replace if you remove the lower fan shroud) My question is that it seems that the battery died awful quick if it was just a bad alternator, combined I didnt even move the car 100 feet. So I am wondering if I may have a short or the battery was sitting for a while at Pep Boys.


In case I have a short, if I check the batteries voltage while its sitting, if I have a short I should notice a drop in voltage right (over the period of a few days)?

[NIK90s13]

Your batt should not be bad from just sitting, If you were running the car with a bad alt. it will drain it, not sitting. If you have a draw on your system you will see a voltage drop over a day or so. To check for a draw, get a test light, make sure everything is off on the car, lights, inside lights ect. Unhook the negitive side of the batt and hook up the test light inbetween the battery and the negitive wire, if the test light, lights up with everything off, you have a draw on the system. To help locate the bad system start unpluging fuses, when the light goes out you have found the area. Sorry this is so long, hope it helps!

[Speed Motoring]

If you can take your battery to autozone and ask them to slow charge your battery. I had a small battery for my car and it died very fast for no reason. Then autozone slow charged it for me and now it's good as ever. Give it a shot and see if it will work. I hope that help.

[seanc]

i am fairly certain the light will not light up without a negative an positive current flowing through it. the best way to test it would be to use a DMM measuring current. there is usually always a small load on your battery from ECU memory, radio memory, clock etc but anything over a couple millamps is a problem

[rancid240]

Grrreat, Im pretty sure there is a short somewhere. I measured 12.6 volts on Sunday, came home monday and after sitting one day Im getting 12.10. Im going to measure today just to make sure (not 100% sure it was 12.6) and log the change. I have removed everything aftermarket except my alarm (but I disconnected its fuse that is a few inches from the battery). Are there any common places for such a short to develop?

[ledzeppelin240]

Yeah removing the neg. terminal and puting a test light inbetween is not the right way to test. Use a clamp on amp meter, or a normal ammeter with one of those quick disconnect battery terminals so the current is never completly cut off. 10-30mA is normal with a max of 50mA draw on the battery. If there is more then start pulling fuses untill the current draw comes down to the allowably amount.

[rancid240]

I tested with my voltmeter Tuesday, got 12.03 volts, and .1-.3 (fluctuating) mA. I didnt disconnect the battery to test.

[ledzeppelin240]

To test amps you need to hook up in series, not parallel.

[rancid240]

To test amps you need to hook up in series, not parallel.


So maybe disconnecting the negative wire, and hooking up the voltmeter from the wire to the terminal? Why avoid letting the current cut off?

[ledzeppelin240]

Some computer circuits will not shut down for 10 minutes or some on some vehicles, the switch just makes it easier you can connect the ammeter in parallel and then just disconnect it and then the current flows through the ammeter then you just reconnect it. Or you could disconnecting the negative wire, and hook up the voltmeter from the wire to the terminal like you said.

[rancid240]

Thanks for all the help led. I think it was my alarm wire, I disconnected the fuse prior, but last night I totally disconnected it. And now only a 4 hundreths drop in voltage in 24 hours.

[ledzeppelin240]

Dam I was going to mention your alarm is probably the culprit but I got sidetracked. That happen to my friends car actually, his car sat for 1 week and would not start then. Other than that he was always driving the car and the battery was never able to drain down.

[rancid240]

OK bump this back up, my battery died again, well not all the way but its to 7 volts. I tried to test the mA by disconnecting the positive and wiring the tester in series, but it only read the same as before, fluctuating between .1-.3 mA. Same when I did that to the negative side. Will I not get a correct mA reading if my battery is not fully charged?

Also, over the weekend, I noticed the cars hatch light was still on (the one that flips on when you open the hatch) even with the hatch closed. I disconnected the bulb, thinking I finally solved the mystery. Well the car was still driveable and sat till today, where it is now at 7 volts. Is there anything else electronically that runs when the hatch is open? Also, when I try to read the volts with the negative side hooked up, it barely measures 1 volt, unhooked it jumps up to 7 volts.

[ledzeppelin240]

Hmmm...

-Ok charge the battery up (above 12.6v)
-Drive (or idle) the car and operate everything electrical.
-then park and make sure eveything is now off.
-disconnect (-) bat. terminal and place ammeter in between (-)cable and (-)battery terminal.
-10mA-30mA reading is normal, anything above 50mA there is a drain.
-start pulling fuses until the draw is below 50mA, then you have found the problem circuit.(if there is stil a draw maybe alarm or short between battery and fuse block?)

I will have to think about the volt readings you are getting and figure out why later...

[NIK90s13]

I agree with ''zeppelin'',Electrical sucks, I just got through finding a phantom draw just like this on a prelude. You need to find the fuse that will kill the draw and then you will know what area circuit to serch.