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Old 04-14-2009, 01:46 PM   #1
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Default diagnosing battery draw with car off...

**UPDATE ** resolved - traced it back to two things - the voltage fluctuation was a bad alternator, and the draw was from where a shop that had moved my wideband had connected it to the cigarette lighter hot wire... Not sure why I didn't catch that pulling fuses but I traced/rewired all my electrical in an attempt to fix this problem, and even got my ancient PAC SWI2 steering wheel control IR to my head unit working again.

Cheers - Rob (Bad30th)


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I've been having to charge up my battery a lot and getting the sweeping gauges/odometer reset lately, so I'm doing some battery troubleshooting.

If I connect the negative terminal up and put a volt meter between the positive terminal on the battery and the positive cable, I'm seeing about a 4-5 amp DC draw with the key off. I'm guessing this is the cause of my dead batteries...

I've tried pulling different fuses and the amp draw never drops...

Any ideas on how to troubleshoot where the draw is coming from ? I've tried the obvious stereo fuses, fuse to my capacitor, etc.

So - A) am I testing this the right way and B) any ideas ? What's a normal amp draw with the key in the off (not IGN) position ?

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Old 04-15-2009, 12:24 AM   #2
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Just a few questions if I may.

Is your amp turning off when you turn the key off?

Usually the remote wire running to the amp needs to be hooked to a powersource that looses power when the key is turned in the off position. If your amp is staying on when your key is off then its definately gonna kill your battery. That would be the first thing I'd check.
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Old 04-15-2009, 09:22 AM   #3
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I have my cap and stereo amp disconnected/unplugged right now, current is still drawing from somewhere with the key out of the ignition. I don't think it's the stereo.

I'm going to take another crack at pulling fuses tonight after work, and look around at where hot lines are connected to all the other stuff on the car (wideband o2, gauges, switches, nitrous solenoids, etc). The wideband O2 was installed by the last shop to work on my car and is the first thing I'll look at tonight, since I'm confident I've never wired anything directly to the battery...

4-5 amps sounds like something pulling a decent amount of power, and it's apparently wired directly into the hot line on the battery and grounded through the battery circuit because the 4-5 amp draw isn't there without the negative terminal connected.

Thanks,
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Old 04-16-2009, 12:00 PM   #4
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Update - with the key out of the ignition/negative terminal connected and with the cap/amp, and wideband O2 disconnected I am still getting about a 5 amp draw between the positive terminal on the battery and the positive cable.

I also pulled the bulb from the trunk light in case it was on, and checked for any other bulbs or lights lit up in the car, no luck.

The only other thing I can think of is that when I put in a new alternator I ran a new heavier gauge wire directly to the battery positive terminal, and taped off/bypassed the stock alt wire. Could the alternator be the drain ?

I have three hot cables coming to the battery - the cap (fuse pulled), the alternator, and the positive cable from the car's wiring harness.

Now that the cap fuse is pulled I get 0 amps between the battery positive terminal and the cap hot wire (which is expected since the fuse is pulled) but still a 5 amp draw from both the alternator hot wire and the wiring harness hot wire.

I will try pulling fuses again today.

Thanks for any ideas, I'd like to get this fixed so my battery isn't always dead or having to be plugged into a charger.

It would be really sweet to have a sticky at the top of this subforum on how to diagnose electrical issues like battery draw and other misc electrical issues... Anyone wanna help start one ?

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Old 04-16-2009, 08:00 PM   #5
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Update...

I pulled every fuse in the three fuse boxes (two underhood and one on driver side dash) one at a time watching the meter, stayed at a 5amp draw through them all. Stereo cap/amp are still disconnected, and wideband is still disconnected. Ugh.

I took it as an opportunity to clean up some wiring by the PCM and resolder/shrink tube some wiring that had clamped quick-connect connections, and clean things up... Next I'll take a look at disconnecting the alternator and see what happens.

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Old 04-16-2009, 08:36 PM   #6
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are you giving the bcm time to power down? i like to push the door locks in on the door jams and wait on the bcm to power down before checking anything. that way you can access everything in the car without waking up the BCM. hope this helps
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Old 04-16-2009, 09:38 PM   #7
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Yep, already considered that - doors are closed on the car (except for when I was testing fuses in the driver side dash fuse panel) and I'll be sure to consider BCM/RAP while testing. I guess if I did fix the drain I could still be measuring current draw from the active BCM/RAP. Thanks for the post...

I disconnected the hot wire from the alternator and the amp draw is still there.

Gonna drink a few beers and ponder it over some TV for the rest of the night I think...

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Old 04-21-2009, 11:03 AM   #8
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Have you found the problem yet? I have a similar situation, although my draw is about 2.5 amps.
Pulled all the fuses, disconnected the alternator and all the relays. Still have 2.5 amps.
Pulling the PCM connections next.
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Old 04-21-2009, 03:51 PM   #9
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No luck so far but haven't spent any more time diagnosing it. I'm going to make a list of everything electrical I've put in the car and start unplugging stuff... If I get far enough to eliminate everything outside the factory wiring I'll start digging around there...

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Old 04-21-2009, 05:35 PM   #10
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i have heard that if your starter blows a fuse it will drain your battery, something to look at.
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Old 04-22-2009, 11:15 AM   #11
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Thanks for the post. The starter/fuse is fine, the car starts no problem...

I'm waiting to troubleshoot more until I get the rest of the car back together and feel like working on it more (brake caliper brackets are off getting powdercoated). Right now I just have the battery disconnected.

The last thing I've thought of to do is re-wire the exciter wire to the alternator. I know the last shop that worked on my car dropped the alternator with the exciter wire connector still attached which snapped the wire, and they repaired it... I don't think that would cause a draw with the key out though, but it probably needs to be looked at anyway.

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Old 04-22-2009, 09:27 PM   #12
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so i have a similar problem right now thats been bugging me. i also just put in a new alternator. my current draw is just over 3 amps. the alternator works fine (charges the battery and puts out 14V with engine running). i pulled all the fuses in my dash panel and left the battery hooked up and still it was drained. finally i discovered that the current draw goes away when i disconnect the alternator fuse in my battery fuse box. i figure there must be a short somewhere in that circuit, but i'm pretty sure its just a wire from the pos terminal of the alternator to the fuse, which is coverred the entire length. any ideas?
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Old 04-22-2009, 11:09 PM   #13
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Quote:
Originally Posted by Bad30th View Post
Thanks for the post. The starter/fuse is fine, the car starts no problem...

I'm waiting to troubleshoot more until I get the rest of the car back together and feel like working on it more (brake caliper brackets are off getting powdercoated). Right now I just have the battery disconnected.

The last thing I've thought of to do is re-wire the exciter wire to the alternator. I know the last shop that worked on my car dropped the alternator with the exciter wire connector still attached which snapped the wire, and they repaired it... I don't think that would cause a draw with the key out though, but it probably needs to be looked at anyway.

Rob (Bad30th)
yes thats the point, thats why its so hard to diagnois, the car will start like normal without any issues but there is still a blown fuse and it draws power while the car is off.
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Old 04-22-2009, 11:22 PM   #14
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^ That makes no sense @ all.

Try pulling the BCM. . . . When I pulled my BCM I found my draw. Well, it was not the BCM at all, but it did help me find it.
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Old 04-22-2009, 11:31 PM   #15
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Quote:
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^ That makes no sense @ all.

Try pulling the BCM. . . . When I pulled my BCM I found my draw. Well, it was not the BCM at all, but it did help me find it.
Im just relaying what i read about someone elses problem, if he pulled all the fuses and there is still a draw it has to be coming from somewhere.
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Old 04-23-2009, 08:26 AM   #16
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Thanks guys, I'll give it a check tonight just for peace of mind.

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Old 04-23-2009, 08:40 AM   #17
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Hmm, I will check those things out when I rewire my alternator exciter wire this weekend.

As for your car, I'd try to double-check and inspect the wire and see if it's rubbed/shorting somewhere maybe... Maybe a short inside the alternator, or something behind it on that hot wire that's connected via that circuit ?
Looked at a schematic for that circuit ?

BTW, I also took another look at how I have my cap wired, since (when not disconnected for testing) it's connected directly to the battery. Using a decently thick hot wire provided by my stereo shop (not sure what gauge), it's connected from battery (+) terminal to a 1' wire, Stinger fuse, runs to trunk through firewall and under trim, connects to second Stinger fuse, then another 1' length to hot terminal on cap. Hot terminal on cap is also connected to stereo (+) with a short 6" line. Neg terminal on cap is connected to a ground I made on the chassis, and to the (-) terminal on the amp. I think that's correct, and I still get the current draw with it all unplugged/disconnected.


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Quote:
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so i have a similar problem right now thats been bugging me. i also just put in a new alternator. my current draw is just over 3 amps. the alternator works fine (charges the battery and puts out 14V with engine running). i pulled all the fuses in my dash panel and left the battery hooked up and still it was drained. finally i discovered that the current draw goes away when i disconnect the alternator fuse in my battery fuse box. i figure there must be a short somewhere in that circuit, but i'm pretty sure its just a wire from the pos terminal of the alternator to the fuse, which is coverred the entire length. any ideas?

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Old 04-23-2009, 08:48 AM   #18
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Just curious, what did your issue end up being ?

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^ That makes no sense @ all.

Try pulling the BCM. . . . When I pulled my BCM I found my draw. Well, it was not the BCM at all, but it did help me find it.
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Old 04-23-2009, 09:57 AM   #19
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Quote:
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Just curious, what did your issue end up being ?

Rob (Bad30th)

Me being a retard. . . . . . . .


I would not give my BCM time to shut down when I was testing the draw. It takes 10 minutes for the BCM to fully shut itself down.

And the battery was dead.

What I did find is that the draw should be @ 0.05 amps after all systems are shut down. Also the 0.05 amps is made up of 0.03 from the fan relay and the other 0.02 is from the PCM itself.



^ Yeah, this took me 3 days to find.
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Old 04-23-2009, 10:25 AM   #20
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Thanks for the info. I'll also triple-double-back-to-back check that it's not the BCM drawing power when testing draw so I don't make your same mistake.

How much current was the BCM pulling when it was alive and you were measuring it ? (LOL please don't tell me 5 amps, haha).

I'm sure my original problem isn't the BCM since whatever it is is draining the battery but I may disconnect it to troubleshoot...

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Old 04-23-2009, 10:25 AM
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