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Old 07-26-2012, 09:06 PM
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bluebee bluebee is offline
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Location: San Jose, California
Join Date: Mar 2008
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Mein Auto: 02 BMW 525i M54 auto 130K
Today there was a decent post about how to test for parasitic current draw over here:
> E39 (1997 - 2003) > Have you searched for parasites lately?

Originally Posted by pleiades View Post
Well, this is the way I've done it, not necessarily the best or correct way, but thought I'd share because it's so easy.

Digital multimeter with a fused 10-amp setting to measure current draw (and equipped with alligator clips)
13 mm socket wrench
Screwdriver (optional)

- Open trunk, lift battery cover, unbolt the chassis end of negative cable (leave battery-end of cable connected to the neg. battery terminal).
- Cover the unbolted neg. cable end with a glove or something to prevent it from contacting the chassis or other metal parts.
- Turn on DMM, connect one probe to battery negative terminal and the other to the chassis (I used the neg cable chassis bolt since it's already "naked.") There may be some sparks....

Optional: Use a screwdriver or something to move the trunk latch to locked position (maybe you can also do this using your key in the keyhole). This part is unnecessary but it turns off the trunk lid light and conserves some electricity during the test. Don't forget to move the latch back to unlocked, open position before trying to close the trunk or you'll break the latch. If you break the latch, don't blame me.

- Watch the DMM. Here are the readings I recorded.
At start of test: 1.5 Amp
After 1 minute: 0.45 Amp
After 16 minutes: 0.027 Amp

When I had my DICE Silverline Pro installed, the final reading was higher, and higher still if I left my Ipod plugged into it. The above readings are for an e39 528i with the alarm disarmed, and with the standard audio system, nav, and CD changer (no DICE or DSP). With the alarm armed, the final reading is only 5 mA higher: 0.032 Amp.

* DON'T mess with the positive battery cable; it is not involved in this test.
* Before closing the trunk, DON'T forget about the trunk latch, if you have moved it to closed position.
* Be sure that your DMM is fused and that you have the probe cables plugged into the DMM and connected properly to utilize that fused protection -- otherwise your DMM fuse will be blown or worse, the DMM will just be rendered into a useless piece of plastic and/or the probe cables will burn. DO NOT accidentally connect the probes to -both- battery terminals with the Amp test setting or you will be inhaling smoke from burning plastic and buying a new DMM.
* If your DMM is the cheap type with an auto-off function (like mine), it will possibly shut itself off about 10 minutes into the test. I watched this happen but was able to quickly flip the dial knob to OFF and then back to the 10 Amp current test position.
* The test as described above only measures the default state of the car at rest, with doors closed. If you want to use this test to search for sources of parasitic drain, you will need to pull fuses one by one -after- the car enters its final sleep state, and watch the DMM for changes. Some fuses, when pulled, will wake the car up and force you to wait anywhere from a minute to the full 16 minutes to continue. Naturally to see and pull fuses in the glove compartment, you may need to have the passenger door open; to mimic closed doors and avoid waking the car when you open a door, keep the passenger door open but squeeze something pliable into the door strikers, closing the switch that lets the car know a door is ajar.
Please read the suggested threads and add value, either by pictures or by descriptions, so the next person stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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