Dead battery parasitic draw fuse #21

[iPee]

1991 318is

I first noticed the car dying after parking it for a while without driving last summer. I thought it may have been a parasitic draw but I wasn’t sure. It got worse in September and the car wouldn’t even start by jumping it. Bought a new battery and everything was good. The most I haven’t driven it was about 2 weeks and it would start up fine, fast forward to April I didn’t drive for a week and the car wouldn’t start.

So far I’ve performed a draw test by disconnecting the positive terminal and creating a series through the multimeter. Some posts I’ve seen people check from positive post and some from negative post. Does this really matter? I read that a normal draw is somewhere from 20-50mA however I have an analog gauge and it shows a reading of 0.4A which is really high unless I’m reading the scale wrong. I plan on borrowing a digital one to verify sometime this week. So I went ahead and pulled fuses and #21 seems to be the culprit.

I know #21 controls a whole bunch of things

Glovebox/Auto-charging flashlight
Ignition key warning/Seatbelt warning
Interior lights
Radio/Antenna
Truck light
Multifuction clock/OBC
Service indicator light

My friend suggest me to test the battery first incase it is a bad battery and can’t hold a charge, before I check for the draws. To do this he said to check for voltage over the next several days. If I test voltage with #21 pulled out I should expect the battery to hold around 12.5 volts over the next several days. Should I perform this test or can I skip this test and start checking the circuits that #21 controls?

To test for which circuit is causing the issue I would need to plug #21 back in and start disconnecting each component to see if the draw decreases?

Things that look suspect at the moment
Tach has been been working on and off.

SI board used to light up the 2 green lights closest to the yellow one. Now it only lights up 1 green closest to the yellow. This happened after my oil change in November 2014 but I did not reset the light or anything. I think the tach stopped working properly at around a similar time as I did the oil change.

Power antenna powers on but it’s stuck and only goes up halfway.

Passenger side interior light doesn’t turn on.

Installed new stereo system over in January 2015 along with amplfiers and a subwoofer.

I have a feeling it may be the SI board but I just wanted to confirm that my logic for testing is correct.


Can't wait to start this mini project lol.


Thanks
Ivan

[pandaboo911]

Check the splice under the drivers side carpet for damage/corrosion. It's a splice joining 9 red/green wires. It runs all the fuse 21 accessories

http://www.bimmerforums.com/forum/attachment.php?attachmentid=253733&d=1217554110

[iPee]

Cool thanks for the tip.

[ELVA164]

My vote is the antenna. When they get stuck they can continue to draw current. Same thing happened to me until I really got intense about cleaning the antenna itself and making sure it moved smoothly.

[iPee]

Haven't had time to perform another current test on the system, so I just tested the voltage on the battery over the last few days. I charged it on Sunday overnight and took the charger off Monday night and also pulled the suspect fuse #21. The readings are as follows

Mon 13.44V
Tue 13.22V
Wed 13.12V

I'm assuming this drop is normal since a battery is only supposed to hold 12.6V. Once it reaches 12.6V it should be able to hold it there for awhile right assuming it's only drawing the normal amount of current while the car is off.

Guess I'll have to check for awhile longer.

[iPee]

Did some testing today and it is indeed fuse 21 which caused a draw of about 80-90mA, took the fuse out and it dropped to 25mA.

So I started disconnecting the interior lights, radio etc...... turns out it was the cluster that was drawing it. The draw stopped once I removed the the blue plug C1. Anyone know what this plug controls? Is my problem still the SI board?

At this point I will likely replace the SI batteries however I was wondering if the C1 plug is related or a completely separate issue. My tach has been finicky and I know it's a symptom of a a bad SI Board however C1 also controls the tach I believe.

[Gregs///M]

From what you are saying, yes the SI board is most likely at fault. Esp since your tach has been acting weird.

Try removing your si board and plugging your cluster back in and I bet your draw will remain low.

[iPee]

I was just about to shoot you an email to see if you had any suggestions. Been looking everywhere for ideas on how to test the board, thanks for the suggestion Greg.

It's late now but I had the SI Board removed a couple days ago, wish I had seen this earlier while I was still at home. Anyway I measured the voltage of the batteries and it was at 3.5V. I've showed the pictures below to couple of my friends and they say the board looks fried. Another one suggested smelling it to see if it has a burnt smell. I did and it smells a little burnt around the middle section.

[iPee]

Also the middle light above the yellow plug is missing, any idea what that one is for?

[iPee]

Did the test as Greg suggested

Tested current without cluster 25mA
Tested current with cluster 25mA
Tested current with cluster + SI Board 80mA

Looks like I know where to head to next. Thank you for the help everyone!

[Gregs///M]

I see no indication of any burnt components on that SI board, all looks fine.

However, I can tell that the SI board batteries have never been changed. So those batteries are around 25-30 years old, consider them dead. Replace them or buy one of our replacements. I will send you money for your original.

Dead batteries alone will cause the current draw, very common.

[iPee]

But if the batts were dead, wouldn't it measure like no voltage? Anyways put in an order for replacement hope I get it soon.

[Gregs///M]

But if the batts were dead, wouldn't it measure like no voltage? Anyways put in an order for replacement hope I get it soon.

No, batteries can have voltage but extremely low current. New batteries have about 800-900 ma. Most dead batteries I see, even with over 3V, have around 10-20ma, dead.

See my article for tons more info on the SI board. Bavrest.com/technical-articles.html

[iPee]

Totally forgot about the current test on the batteries on the board. Well don't have access to tools to remove batteries anyway so. Thanks for the heads up.

[iPee]

Got the new board, everything works now!