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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > Super hard power drain to find :( Please help



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      06-17-2019, 09:20 PM   #1
nasu
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Super hard power drain to find :( Please help

Hi guys,
Been fighting this from when I purchased the car, I wish I knew this eh well I am learning. I did pull out all fuses, relays, computers etc I couldn't find the drain until this red cable that goes from rear fuse box to the front fuse box, as soon as I disconnect that all drops off. Please watch the video. I even connected it straight to the battery it doesn't make any difference battery still drains.

What do you think? does the cable split anywhere or it's one piece ? I found one on ebay looks like one piece

I also got an E93 but that one is fine, thanks God, posting in E90 as looks like a bigger community in E60 they don't really know

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      06-18-2019, 12:15 PM   #2
nasu
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looks like that cable is one piece and part # 61119243091



how can it draw power if it's disconnected on the other end ? If cable is broken inside it can't draw power... unless somewhere on the line someone decided to tap in right ?
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      06-18-2019, 12:34 PM   #3
Tambohamilton
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Whatever your power drain is, is connected to the other end of that cable. So that could be anything connected to the front fuse box...which doesn't narrow down your problem much.

Can you connect an ammeter in series between that cable and the battery, to measure how much current is flowing with the car on standby (ignition off, lights off, etc.)
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      06-18-2019, 12:42 PM   #4
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Measure the resistance of that cable, as well as the resistance to ground at each end. That should rule in/out physical damage or splicing of the cable, which should definitely narrow your search.
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      06-18-2019, 01:45 PM   #5
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I did measure it's about between 100 and 250mA draw from that cable only. I don't think it's damaged as it can carry power fine to the rest of the module in the front fuse box and I measure the voltage it`s as much as the battery from his front end and ground
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      06-18-2019, 01:46 PM   #6
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Quote:
Originally Posted by nasu View Post
I did measure it's about between 100 and 250mA draw from that cable only
mA is not a unit of resistance
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      06-18-2019, 01:51 PM   #7
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that was for Tambohamilton question on how much draw is on the cable. resistance is fine, cable is not broken
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      06-18-2019, 02:31 PM   #8
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Quote:
Originally Posted by nasu View Post
that was for Tambohamilton question on how much draw is on the cable. resistance is fine, cable is not broken
Consider using the quote button to avoid confusion like this.
Does the cable show infinite resistance to ground?
Something weird is going on.
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      06-18-2019, 02:35 PM   #9
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Quote:
Originally Posted by nasu View Post
I did measure it's about between 100 and 250mA draw from that cable only. I don't think it's damaged as it can carry power fine to the rest of the module in the front fuse box and I measure the voltage it`s as much as the battery from his front end and ground
Yep, that's a power draw alright - it should be more like 10-20mA.

It's still drawing that much with every fuse and relay pulled?
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      06-18-2019, 02:58 PM   #10
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yes it does still draw that much. The only time it draws less is as soon as I pull the red positive b cable out, even tho I disconnected it from the other end (front fuse panel) so it must be 2 things
1. the previous owner played with it and maybe he tapped in the cable along the way with something.
2. less probably. the cable at some way is uncovered and touching the other cables or the body of the car ? ..

I guess it will be a tear off removing the passanger front seat and carpet etc and start removing that cable before I spend 300$ on a new one as I might discover along the way something interesting... damn it it's not even a lot of amps but enough to put my discharge my battery in a week or 2 and slowly destroy my 2 year old battery.

Funny enough I see no label on that cable I get a feeling someone played with it before me I just don't know .. time to find out ..
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      06-18-2019, 04:54 PM   #11
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So, what's the resistance between that cable and ground, with everything disconnected from the cable?
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      06-19-2019, 12:52 PM   #12
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Quote:
Originally Posted by Tambohamilton View Post
So, what's the resistance between that cable and ground, with everything disconnected from the cable?
Literally the third time we had to ask him to do this basic diagnostic step.
I'm unsubscribing. Good luck!
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      06-29-2019, 08:36 PM   #13
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Thanks everyone, it's fixed. Someone tapped into that red power wire and found it , remove it , unfortunately I started from the front and removed the chair and a lot of other things. I measured resistance with ground and it was high about 7.5 ohms, way to high. Thanks everyone for helping out with this, feels so great even tho I spend 20 + hours I saved big bucks and learned a lot. Sorry for my "french" I was very pissed off to find it there...

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      06-30-2019, 02:12 PM   #14
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Glad you found it! Did you find what the extra wire was connected to?

P.S. Just to be properly correct, the resistance from the battery cable to ground is *low* at 7.5ohm. This indicates a rather direct connection to ground, which will draw more current/power from the battery. What would have been better is a *high* resistance, indicating a resistance to current/power draw.

Last edited by Tambohamilton; 06-30-2019 at 02:17 PM..
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