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Andre Asselbergs

E66 parasitic drain

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Good day gents. First post, joined your forum today. As per title, I have a problem with my 2003 760Li and the battery going flat. As a precursor, I have a brand new battery that has been paired with the car. The problem has been evident for a couple of years now and since well before the battery was replaced so I think it fair to assume the battery is not the problem.

I’ve been going down the path for a while of having a multi meter in line and pulling fuses one at a time without really finding anything substantial. I read another thread similar to this where the poster talked of a drain of 0.45 amps or so. God, I wish!

Yesterday I took both terminals off the battery and connected them to a jump-start pack. Got a drain of 14.5A after switching everything off (including triggering the boot lock) but this was the navigation DVD running. It stopped after a few minutes, draw dropped to about 6A. Draw started tapering off after another 10 minutes, I guess as systems were shutting down. After 20 minutes it was down at 0.01 amps. So I can live with that (clock, etc.) and knew that I had discovered nothing.

Frustrated, I connected the positive to the battery with the multi meter still in line on the negative and the process was the same as above (shutting down over time) but it stopped tapering off at around 4.5A and is still steady at that level after a few hours. No wonder the battery goes flat!

Does anyone have any idea why the connection to the battery would differ from a connection to a jump-start pack?

This on-going issue is really spoiling an excellent car and any help you boffins can provide would be highly appreciated.


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Update: I went through both fuse boxes again (draw on the ammeter around 5.5A) withdrew every fuse, no change. So I went back to the boot and disconnected the “secondary” cable from the battery positive (leads up to the power module). Drain dropped to less than 1/4A.

Reconnected the cable, went to the power module. Pulled the cable that feeds the fuse box in the boot. No change. Pulled the cable that I assume feeds the fuse box in the glove box. Drain dropped to 1/4A again. So clearly the problem has to do with that area. But with all fuses removed from that fuse box, what is left to check?

I’m obviously missing something.

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