Why does my battery keep going dead?
Why does my battery keep going dead? Okay, here is what is happening. If my car sits for more than a day without being driven, the car will not start. The volts indicate they are very low when the key is turned (without starting the car). The previous owner said that he always left the car on a battery tender when it wasn't being driven which makes me think he had problems too. Things that have been done to the car: I have a 200 Amp aftermarket new alternator, new Optima Red top battery, 4 gauge charge cable from alternator, 1000 watt amp powering 2 12'' subs. The car was having this problem before I installed all of the above. So where should I start looking first. Could a bad exciter wire cause this? That was one thing i didn't replace when I replaced the stock alternator. I replaced the stock alternator because it had a bad voltage regulator. Your help would be greatly appreciated!
After you charge it and then get it started, how does it run?
A bad excitor wire will cause the alternator to simply never start charging, so the battery will drain while you're driving it after you charged it and started up.
Can't hurt to try a new one. $12.50 and 30 minutes of your time.
http://cgi.ebay.com/ebaymotors/LS1-A...Q5fAccessories
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A bad excitor wire will cause the alternator to simply never start charging, so the battery will drain while you're driving it after you charged it and started up.
Can't hurt to try a new one. $12.50 and 30 minutes of your time.
http://cgi.ebay.com/ebaymotors/LS1-A...Q5fAccessories
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Once the car is started it runs fine. The voltage meter is a little past 13 when driving in the daytime and around 14.7 at nighttime with the headlights on. Is there anything else I should check?
If you lose the battery charge while its just sitting, you either have a bad battery or a short somewhere thats drawing power all the time.
I know its new but go get the battery checked while its in the car. Could just be a dud.
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Im chasing the exact same problem. My alt is very close to going out (been tested twice and barely passed both times) so Im going to change that. I have nothing that can possibly be drawing power and Ive even tested.
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I'd start checking for a key off battery drain - check the current draw with all of the fuses in place, and then start pulling them one by one and checking the current each time. IIRC, I think 10-20mA is about a normal draw for these cars, key off. If you get something higher than that, then you need to figure out which circuit it is and go from there.
I chased something like this years ago, and it ended up being my HPTuners interface that I was leaving plugged into the OBDII port. I didn't think it pulled any power, but it certainly did, and it was enough to drain the battery if I didn't start it for ~3 days. Kind of a useless anecdote, but it ended up being something completely unexpected, and completely my fault.
I chased something like this years ago, and it ended up being my HPTuners interface that I was leaving plugged into the OBDII port. I didn't think it pulled any power, but it certainly did, and it was enough to drain the battery if I didn't start it for ~3 days. Kind of a useless anecdote, but it ended up being something completely unexpected, and completely my fault.
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You could check to see if your excitor wire is working or not by disconnecting your negative battery wire while the engine is idling. If it stalls the alternator isn't doing anything. Good chance its the excitor wire. But it could be other things. But if the alternator checked out ok, thats probably it.
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When I say that it tested good, Im saying that it charges at around 12.7 volts instead of 14.7. Its going to get changed soon as well as a new exciter wire.
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Verdad Gallardo I'd start checking for a key off battery drain - check the current draw with all of the fuses in place, and then start pulling them one by one and checking the current each time. IIRC, I think 10-20mA is about a normal draw for these cars, key off. If you get something higher than that, then you need to figure out which circuit it is and go from there.
I chased something like this years ago, and it ended up being my HPTuners interface that I was leaving plugged into the OBDII port. I didn't think it pulled any power, but it certainly did, and it was enough to drain the battery if I didn't start it for ~3 days. Kind of a useless anecdote, but it ended up being something completely unexpected, and completely my fault.
I chased something like this years ago, and it ended up being my HPTuners interface that I was leaving plugged into the OBDII port. I didn't think it pulled any power, but it certainly did, and it was enough to drain the battery if I didn't start it for ~3 days. Kind of a useless anecdote, but it ended up being something completely unexpected, and completely my fault.
You don't need a scan tool for this one - just a simple multi-meter with a fused side for reading current.
Ok so I got a good multimeter and tested everything again. These were the readings that I got. I took them on VAC 200
Drivers side fuse box:
Fuse #7 Power Accy 24.2
All these are under hood:
HLDR Horn 25.2
RH HDLP DR .2
LH HDLP DR .2
PCM Batt 23.3
Drivers side fuse box:
Fuse #7 Power Accy 24.2
All these are under hood:
HLDR Horn 25.2
RH HDLP DR .2
LH HDLP DR .2
PCM Batt 23.3
Voltage AC.
Manual says that its shows the resolution at .01V.
Im correct in thinking that I dont need to check for the current because this doesnt happen when the car is on. Its only when its off so I need to check for a voltage draw from the battery when the car is off right?
Manual says that its shows the resolution at .01V.
Im correct in thinking that I dont need to check for the current because this doesnt happen when the car is on. Its only when its off so I need to check for a voltage draw from the battery when the car is off right?
Voltage AC.
Manual says that its shows the resolution at .01V.
Im correct in thinking that I dont need to check for the current because this doesnt happen when the car is on. Its only when its off so I need to check for a voltage draw from the battery when the car is off right?
Manual says that its shows the resolution at .01V.
Im correct in thinking that I dont need to check for the current because this doesnt happen when the car is on. Its only when its off so I need to check for a voltage draw from the battery when the car is off right?
TECH Addict
Joined: Jun 2009
Posts: 2,012
Likes: 0
From: Tulsa, OK
The VAC is the giveaway to what he's doing. That means he was using the volts AC scale. Evidently he doesn't understand the difference between AC and DC, or voltage and current. The readings would be meaningless if this is the case.
Yes, you need to check for current draw with the key off. Whichever circuit is causing the problem will show a reading of some sort, and if it kills the battery overnight it will be a fairly significant draw. Using the voltage scale won't tell squat for a problem like this.
Yes, you need to check for current draw with the key off. Whichever circuit is causing the problem will show a reading of some sort, and if it kills the battery overnight it will be a fairly significant draw. Using the voltage scale won't tell squat for a problem like this.
Voltage AC.
Manual says that its shows the resolution at .01V.
Im correct in thinking that I dont need to check for the current because this doesnt happen when the car is on. Its only when its off so I need to check for a voltage draw from the battery when the car is off right?
Manual says that its shows the resolution at .01V.
Im correct in thinking that I dont need to check for the current because this doesnt happen when the car is on. Its only when its off so I need to check for a voltage draw from the battery when the car is off right?
You need to check for current draw, key off. Disconnect either the positive or negative battery terminal, and leave the other one in place (still connected to the battery). You will hook the multimeter up in series, basically completing the connection from the battery cable to the battery, only you'll be able to see the current flowing through the multimeter since it is now in line between the battery cable and the battery terminal. You'll know you did it correctly when you make the connections with the multimeter and you hear some clicking of the various systems getting power again. This is also why you'll need to use the side of the multimeter that is fused - when I first made the connection on mine, it would draw upwards of 1 Amp for just a split second, then it would settle down.
If you need help with this, just send me a PM and I'll try to walk you through it.
I got it figured out.
I switched the grounds on the battery ground to body and it works great now. Just put the battery ground on the bottom so it would have good contact and I get around 14 volts at idle now.
Still might need an alt but we'll cross that bridge when I get there.
I switched the grounds on the battery ground to body and it works great now. Just put the battery ground on the bottom so it would have good contact and I get around 14 volts at idle now.
Still might need an alt but we'll cross that bridge when I get there.
On The Tree
Joined: Jun 2008
Posts: 138
Likes: 0
I have the same issue. Battery goes dead after a couple of days. I disconnected the ground from the battery, set my multimeter to read milliamps. hooked one line of the multimeter to the disconnected battery ground cable, the other to the negative terminal on the battery. i get a reading of .71 milliamps of draw. what should i do next? Thinking i will start pulling fuses to see if the draw goes down. i also read somewhere that some newer vehicles will have a higher draw once they are first turned off, then 20 minutes to an hour later, the draw goes down? Is this true with our cars? Also heard that i should check the battery for any a\c current reading with the car started? The article said that a bad diode in the alternator can cause a\c current to leak, and that any a\c reading with the car started, means a bad diode in the alternator. I read that this could cause tha battery to drain with the car off?
Teching In
Joined: Oct 2007
Posts: 14
Likes: 0
From: Modesto, CA
I had this same problem Do you guys have an after market CD changer? I have one that was in the car already when I bought it. It was installed in the back of the car on the opposite side of where the spare tire sits. The people that installed the 6 CD changer just tied into a wire that was running to the rear of the car. I think that it must have been tied into an "always-hot" wire like the brakes. Ever since I unplugged the CD changer, the car holds a charge. Mine may be the only situation like this, but just thought I would share.