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Old 11-15-2012, 04:57 AM   #1
PB4
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TJ Battery drain, 0.8amps key OFF

Hi guys, this is my first post !

got a dead battery twice in a row so started investigating, found some nice info here.

Key off, the anmeter shows 0.8amps, I tried removing fuses and found that Fuse (old no7 when removed drops the drain to 0.15.
If I put fuse back in I can hear the relay right next to the fuse box slightly bellow (behind glove box) it clicking on.
Now if I investigate further I also found that disabling the passenger airbag with the key switch in the dash drops the drain from 0.8 to 0.4. (couldn't find a way to disable the driver airbag, I though maybe 0.4 + 0.4 = 0.8)

Any thoughts ?
thanks

Edit : 2004 Jeep wrangler, new battery, fully charged the day before with in home charger.

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Old 11-15-2012, 05:01 AM   #2
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Just a thought, but do you happen to have an aftermarket alarm installed? Back when I was a mechanic (way back), these tended to be the biggest cause of parasitic drains.

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Old 11-15-2012, 05:31 AM   #3
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Another possibility, my Mom's Tahoe was having the same problem. I traced it to the a/c relay being stuck.
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Old 11-15-2012, 08:38 AM   #4
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thanks, will have a check when I'm back home, where is the A/C relay located ?
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Old 11-15-2012, 08:59 AM   #5
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Hook up the ammeter and open the fuse box under the hood pull the a/c relay and see if the current draw changes. If not try the other relays but the a/c is most likely the culprit in my opinion.
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Old 11-15-2012, 09:23 AM   #6
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do you have an aftermarket radio ? Have seen improperly wired radio drain battery.
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Old 11-15-2012, 09:25 AM   #7
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How long are you waiting before you take the measurement? Many electronic modules like the BCM and PCM can take several minutes before they fully shut down. Close all the doors, make sure everything is off and connect your multi-meter in series with the negative lead. Wait at least a few minutes and check the reading on the meter. If it's above .04 amps or 40 milliamps, you've got a problem and you should start by disconnecting anything aftermarket. Pulling fuses and then re-installing them may reset a module, meaning you would hear some clicking and the draw would go back up until that module shuts down. Always take the measurement a few minutes after you pull/replace a fuse; your readings may or may not be accurate if you don't.

When you say you got a dead battery twice in a row, was it the same battery,or did you replace it after the first, only to find the new one dead shortly after? Once a battery dies once, it never recharges to it's full potential. If the same battery died twice without being properly trickle-charged in between, it could still just be a bad battery.
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Old 11-15-2012, 09:33 AM   #8
Knows a couple things...

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One more thing to keep in mind is that there will always be some battery draw due to the PCM (engine computer) and even a very small amount just for the memory & clock in the radio.
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Old 11-15-2012, 10:02 PM   #9
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thanks guys, unfortunately I'm out of town until tomorrow but I'll get back under the hood as soon as I can, yes 0.8amps was the constant drain minutes after connecting the good battery (my other car's). I was surprised to see that pulling some breakers would actually increase the drain (sometimes above 3 amps) but never waited more than 30 secs, I thought that was long enougth for it to settle, I'll try again.

about the dead battery, I understand, but the fact is my car is draining nearly 1 amp when everything is off, so that is a separate problem from the battery. I have fully recharged it now, and will leave it disconnected for 24hrs, we'll see when I come back.

Yes aftermarket radio, Kenwood, I'll try to disconnect the back connector as well.
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Old 11-16-2012, 01:20 AM   #10
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Exactly which fuse are you removing to drop the the draw down? The only fuses in the fuse block that should even have power to them with the key off is 1,2 & 3.

If any others have power with the key off there might be a problem with your ignition switch.
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Old 11-16-2012, 08:13 AM   #11
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Is this an ongoing problem or just started ? I don't think the radio will draw that much. Check all lights sometimes brake lights stick on. Is this a new jeep to you ?
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Old 11-16-2012, 08:42 AM   #12
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Quote:
Originally Posted by Jerry Bransford View Post
One more thing to keep in mind is that there will always be some battery draw due to the PCM (engine computer) and even a very small amount just for the memory & clock in the radio.
This. The FSM says between 5 and 25 miliiamps. 0.005 and .025 amps respectively. You've definitely got something going on. Check the things mentioned above.
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Old 11-16-2012, 09:19 AM   #13
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Originally Posted by s14sh3r View Post
This. The FSM says between 5 and 25 miliiamps. 0.005 and .025 amps respectively. You've definitely got something going on. Check the things mentioned above.
Wow, I don't have an owner's manual for my TJ, but I work in 12v electronics for a living. A typical vehicle's acceptable standby parasitic current draw is around 30-40 milliamps, or .04 amps. .005 amps is virtually nothing... I would be surprised if anyone ever saw that small of a reading. I know the Jeep's electrical system is pretty basic, but even a clock's memory would pull more than .005 amps.

The MECP(Mobile Electronics Certified Professional) study book states that most good batteries can handle a current draw of up to .04 amps on standby, assuming the vehicle is driven at least every few days. To the OP: I would try to get a draw of less than .04 but not worry so much about getting those very low numbers that you may never achieve. I would certainly agree that .8 amps is way too high; just be sure to wait a solid 5 minutes after any change to take your readings.

Another tip, a typical automotive SPDT relay will draw around 250 milliamps, or .250 amps when energized... you may have a relay or two sticking with a reading as high as yours.
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Old 11-16-2012, 01:07 PM   #14
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Quote:
Originally Posted by eboven View Post
Wow, I don't have an owner's manual for my TJ, but I work in 12v electronics for a living. A typical vehicle's acceptable standby parasitic current draw is around 30-40 milliamps, or .04 amps. .005 amps is virtually nothing... I would be surprised if anyone ever saw that small of a reading. I know the Jeep's electrical system is pretty basic, but even a clock's memory would pull more than .005 amps.

The MECP(Mobile Electronics Certified Professional) study book states that most good batteries can handle a current draw of up to .04 amps on standby, assuming the vehicle is driven at least every few days. To the OP: I would try to get a draw of less than .04 but not worry so much about getting those very low numbers that you may never achieve. I would certainly agree that .8 amps is way too high; just be sure to wait a solid 5 minutes after any change to take your readings.

Another tip, a typical automotive SPDT relay will draw around 250 milliamps, or .250 amps when energized... you may have a relay or two sticking with a reading as high as yours.
I agree, the .005 is a very low figure. I'm guessing that would be for the PCM only on a model with no radio.

The service manual states:
Quote:
The 25 milliamperes are needed to
supply Powertrain Control Module (PCM) memory,
digital clock memory, and electronically tuned radio
memory.
Anything other than the stock radio and that number will go up
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Old 11-16-2012, 11:44 PM   #15
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ah ah, got it, key off, all fuses & relays in, drain : 1.08 amps.

I pulled everything, scratched my head, then saw that white wire in the picture, was a bit squeezed, it made contact with the B(+) connections of the PDC box, once lifted a bit, drain : 0.08, ok still twice the 0.04 suggested above but I didn't waited long as well, maybe it would have dropped a bit more after couple minutes.




Now question is, what the h@@@k is that obviously modified wire here for ? It connects under the HBL relay and goes into the obviously added fuse outside the PDC box (above it in the pics), then the wire goes into the group of wires which are wrapped together (pardon my lack of technical vocabulary, English is not my mother tongue)
Does that rings a bell as a common modification ? I had a hard top that I removed (no bikini either at the moment, completely naked )

thanks for all your inputs
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Old 11-16-2012, 11:50 PM   #16
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oh, just a small clarification, I bought this jeep a week ago, not from a dealer obviously, so I have no info on previous history or any mods done, it was pretty much a buy "as is" deal. (guy told me he never had a battery problem.. replaced 2 months ago... yeah right)
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Old 11-17-2012, 12:02 AM   #17
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got it, traced it down to the aftermarket KC lights that have been installed... will isolate the wire and good to go, drain is now 0.02
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Old 11-18-2012, 09:40 AM   #18
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Originally Posted by cixpak88 View Post
Just a thought, but do you happen to have an aftermarket alarm installed? Back when I was a mechanic (way back), these tended to be the biggest cause of parasitic drains.
Thanks for raising that possibility...my 2000 Sport has been eating a battery a year for the past 3 years or so(most recently this morning!), and the alarm freaks out so much I had to disable its connection to the siren. So I'm pretty sure the alarm is the problem. How complicated is it to remove an after-market alarm? I don't need it anymore anyway ..... Thanks!

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