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Old 12-01-2010, 09:26 PM   #1
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Default Something is draining my battery overnight...

Every morning it's completely dead. When I leave for for lunch it starts fine, leave work for the day it starts fine, leave the gym it starts fine. By morning it's dead as a door nail. How do I diagnose this? Car is equipped with MSII, I've already disconnected the amp so that isn't it. I really haven't added any other electronics.


BTW, my batter is only 6 months old and MS says my alternator is doing just fine.
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Old 12-01-2010, 09:31 PM   #2
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How are you starting it when it's dead? The same thing was happening with mine, it would mysteriously COMPLETELY die, turned out the battery terminal clamp was cracked and would sometimes not be connected then i'd jump it which would make the terminal touch. Fixed it with a new terminal and voila. Probably a long shot, but its worth checking.
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Old 12-01-2010, 09:32 PM   #3
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How are you starting it when it's dead? The same thing was happening with mine, it would mysteriously COMPLETELY die, turned out the battery terminal clamp was cracked and would sometimes not be connected then i'd jump it which would make the terminal touch. Fixed it with a new terminal and voila. Probably a long shot, but its worth checking.


I have to use jumper cables and my truck.
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Old 12-01-2010, 09:37 PM   #4
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Originally Posted by levnubhin View Post
How do I diagnose this?
With a multimeter capable of reading DC current. Pull a fuse and stick the probes into the hole to complete the circuit. When you find the one that's got dark current on it, you know where to look.
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Old 12-01-2010, 09:43 PM   #5
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With a multimeter capable of reading DC current. Pull a fuse and stick the probes into the hole to complete the circuit. When you find the one that's got dark current on it, you know where to look.
I was with you until you got to "dark current" And Google isn't helping me with that.
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Old 12-01-2010, 09:44 PM   #6
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Current passing through a circuit when it ought to be "dark" (off.)

The radio will draw a milliamp or three to keep the memory alive, ditto the ECU. So will an alarm if you have one. That should be about it.


You can stick the meter inline with the battery itself for starters, just to make sure that this is in fact the problem, and you're not simply dealing with a battery full of koala **** instead of electrolyte, or something similarly annoying.
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Old 12-01-2010, 09:50 PM   #7
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Cool, first stop tomorrow will be to buy a meter.

Thanks Joe.



I don't know if this means anything but I was poking at the fuses under the dash with a light tester and the defroster fuse had current going through it with the key off. Is this normal?
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Old 12-01-2010, 09:58 PM   #8
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no
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Old 12-01-2010, 10:05 PM   #9
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Shouldn't be.



The relay's coil is supplied by the IG2 position of the keyswitch, and thus, that relay should be open when the key is off.

Try leaving that fuse out tonight and see if the car starts in the morning.
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Old 12-01-2010, 10:07 PM   #10
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Will do, thank you sir.
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Old 12-01-2010, 10:09 PM   #11
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Joe with the ninja edit.
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Old 12-02-2010, 03:45 AM   #12
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I was thinking kind of what Joe said. In a similar situation, I stuck an ammeter in series with a battery cable and started pulling fuses to find where my problem was.
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Old 12-02-2010, 09:05 AM   #13
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What's the word turd?
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Old 12-02-2010, 09:15 AM   #14
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according to the '99 manual the defog fuse is hot at all times. however if there's power going through the rear window defroster relay, that could cause issue. check for voltage on the blk/red wire coming out of that.

but, like you said joe, the relay should be off. IF there was voltage through the a/c fuse AND defog fuse, then that would clearly be an issue.

He wasnt having issue until he made a fix on his harness, where I screwed up his a/c activation. I went through the diagrams to figure if that could be the cause but I see no way that wiring would cause any relay to stay activated when teh car was off. And it would be easy for him to see the clutch spinning or a/c fan running.
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Old 12-02-2010, 09:50 AM   #15
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So Uhh yea, I left the defroster fuse out and she started rigt up.
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Old 12-02-2010, 10:10 AM   #16
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Phil told me last night that his car is wired for defrost but he doesn't actually have anything in his car with a defrosting element. Would that entail a bad switch? Looking at the diagram Joe posted it looks like that and the condenser are the only things that can bypass the heating element to ground. Not sure how the condenser plays into that mix.
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Old 12-02-2010, 10:12 AM   #17
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hmmm.

Maybe your rear defroster switch is broken and not auto shutting off? It looks like to send power through the relay would require the switch to simply ground the relay...if the switch was stuck on, the defroster relay would be always open.

EDIT: yeah if that's the case, whatever the condenser is is drawing power.


Easiest check would be to put the fuse back in and check for power at the condenser (appears to be behind the driver seat near the floor).
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Old 12-02-2010, 10:12 AM   #18
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Probably a stuck relay, then.
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Old 12-02-2010, 11:02 AM   #19
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'Condenser' is just an older term for 'capacitor'. From the sound of things, and looking at the schematic above, I'd say the cap is shorted.
If your car doesn't have a defrost element, just pull the defrost relay and be done with it. It's probably 'stuck' anyway.
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Old 12-02-2010, 11:07 AM   #20
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Phil said he heard a click when he pulled the fuse. I have a feeling the relay was stuck closed and removing the constant power source from it finally opened it.

He confirmed this morning that there was no power at his defroster connector with the fuse put back in.
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