Parasitic Drain - Not the usual suspects, but the Sunroof ??

[Effduration]

Hi Folks,

Just sharing....

I went through a parasitic drain test on my '05 E53 X5 3.0 150k with panoramic sunroof.

I rigged up a battery shut-off switch on the negative battery terminal and drilled small holes on either side of the switch just big enough to accept probes from my multi-meter...holes NEED to be a tight fit for good contact.. That way I can force current through my multimeter by flipping the switch...See photo.

Anyway using my multimeter set in the 10A mode, and the X5 in sleep mode after 16 minutes, I was pulling 130 milliamps..Too High!

Rather than pull fuses, I started testing for Millivolts across all the fuses in the glovebox..there should be zero voltage across the fuses..On the bottom row, I found fuse 58, 20amp for the sunroof (only) ....It was pulling 0.3 millivolts, which equates to about 90 milliamps.. I pulled fuse 58 and my multimeter showed just 40 milliamps at the Battery on sleep mode.. Perfect!

I may do some more research on the sunroof switch or module in the Spring..it's cold here now...but I was interested in just puling the sunroof fuse anyway...Given the reported problems with the Pano sunroof, I don't use it and don't want family members using it...Now they can't..

If anyone is interested in article by BMW CCA's own "Hack Mechanic" Rob Siegel (a former E53 owner) on parasitic drain testing, here it is:
https://bimmerlife.com/2023/02/06/he...rasitic-drain/

[80stech]

Good work! There is no way you can calculate the milliamps from millivolts though unless you know exactly what the resistance is across the fuse/holder (points you are measuring)
I've noticed that often there is a code for the sunroof needing to be initialized after the battery has been disconnected, maybe try that for kicks, you never know!

Instead of drilling holes maybe run a couple of extension wires

[Effduration]

Originally Posted by 80stech

Good work! There is no way you can calculate the milliamps from millivolts though unless you know exactly what the resistance is across the fuse/holder (points you are measuring)

I used the chart found here:
https://www.focusst.org/attachments/...ts-pdf.394759/

They seem to have calculated the resistance for several different types of fuses with different amperage values. They then calculated (estimated?) milliamps at different voltage readings.

I used the the table on the last two pages for "standard fuse"

[cn90]

I posted the trick and the proper Ammeter in the E83 X3
forum.

I helped a friend with his 2004 X3 and the battery drain was
the sunroof motor. Removed the fuse for sunroof and problem
was solved.

[80stech]

Ahhh, yes that all makes a difference, i figured you must have some kind of chart Really no need to be accurate anyway and as long as a person is using a multimeter with high impedance, close enough to find a problem
Even without a chart, comparing fuses of the same amperage should be enough to get pointed in the right direction.

Yes, now I see what you meant by drilling holes As long as the connection is good and tight so a person doesn't risk taking the car out of sleep

When I was checking my e70 I drilled a hole in the battery terminal and put a screw and wire to it so didn't need to install the battery switch.

[andrewwynn]

Good tips both the millivolt across fuse and the cut off switch. One nice thing with the cutoff switch you could get more actuate milliamp readings on mA scale by opening the switch after the car jumps off the high current at shutdown. (Typically the car will be pulling multiple amps and would blow the low scale fuse). Oh also striking holes for the probes that's great!