Detailed step by step diagnostic DIY ... dead battery ... parasitic current drain

Originally Posted by 540iman

My father died when I was almost 9

I'm very sorry about that. You're a good man, and he would be proud of you now.

Originally Posted by 540iman

I thought you had two FSUs that are bad and did not want to buy a third until you knew #2 was definitely bad.

What drives me more than fixing the bimmer (which is as simple as buying a new FSU) is HELPING OTHERS diagnose and fix theirs.

And, the KEY to helping others is putting the pieces together (as you did with the ABS control module diagnostic tree) to determine how to tell WHAT went wrong (inside the FSU).

Originally Posted by 540iman

I am replacing the guibo; Want to know from someone who has done this job themselves.

Unfortunately I have not so I can only refer to the threads. Sorry. But there are folks in the threads who have done it, so they'd know best.

- How a worn drive shaft, flex disc, center bearing, or "giunti Boschi", aka giubo, can cause the vehicle to vibrate (1) (2) (3) (4) & how to repair the rear driveshaft seal by the differential (1) & how to repair the inner constant velocity (CV) half-drive shaft (1) & how to replace motor mounts (aka engine mounts) and transmission mounts (aka holders) on the BMW E39 I6 (0) (1) (2) (3) (4) & for the E39 V8 (1) (2) (3).

Thank you for the kind words Blue. I just want to understand which FSU you are going to reinstall and what it was doing wrong when you last removed it? Do both of your FSUs have the same failure mode? I.E. they acted the exact same way when they failed? Did the blower go to high speed, stop running, or work with huge battery drain? Just trying to understand. The one I would fear the most would be the one that still controls the fan speed, but never goes to sleep or goes to a place where it only draws excess current occasionally. I'm not sure I have my understanding correct. Did you put them side by side on the desk and test the resistance point to point of each one and see any significant difference?

Originally Posted by 540iman

Do both of your FSUs have the same failure mode?

Nope.
The original GKR / Siemens / BMW all-aluminum FSU failed on 1/26/2009 as per this thread:
- How to diagnose what's wrong with a battery that goes dead once a month?

There were no initial symptoms except for a repeated dead battery overnight (battery & alt were fine). Three days later, I had learned to listen for the fan motor with the key removed, so I had bought a new (acm) FSU.

On 2/2/2009, I tested the old and new FSU side by side:

RESISTANCE FROM TERMINAL TO ALUMINUM FINS:
#4 #5
#1 #2 #3

pin 1 OLD: 600 K ohm NEW: 11.2 ohms
pin 2 OLD: 3.02 M ohm NEW: 1.22 M ohm
pin 3 OLD: 2.219 M ohm NEW: 608 K ohm
pin 4 OLD: 2.136 M ohm NEW: 602 K ohm
pin 5 OLD: 3.05 M ohm NEW: 1.277 M ohm

Notice that these measurements were NOT consistent with my measurements in this thread above.

The primary symptoms for the second (acm) FSU were, again, the battery drained successive nights; however I could never hear any oddities of the fan. And only once, was I able to see the 14Amp spikes every three seconds which you see earlier in this thread.

Pulling the fuse and/or the FSU stopped the battery drain.

Originally Posted by 540iman

The one I would fear the most would be the one that still controls the fan speed, but never goes to sleep or goes to a place where it only draws excess current occasionally.

I think that's what I have, but, further tests are in order.

Originally Posted by 540iman

Did you put them side by side on the desk and test the resistance point to point of each one and see any significant difference?

Not only is the pin-to-pin and pin-to-fin resistance vastly different between the two bad FSUs, side by side, but also, the acm FSU doesn't read the same thing it read when I first tested it. All tests were done with the same DMM and test leads.

It's a pretty simple test, so I couldn't have screwed it up.

My pensive conclusion is that both FSUs went bad in different ways, yet both exhibited nary a symptom save for the dead battery overnight.

So they both continued to control your fan what seemed to be to the proper speed. One of the FSUs however allowed the fan to run probably slowly after car was shut off. Is this correct? Problem with the pins you tested are that the "quills" are likely not even at ground potential so testing the resistance from the quills to anything is a waste (I know you tried your best). It would be pins 1-2, 1-3-1-4 and 1-5 and then 2-3,2-4, and 2-5 and the3-4 and 3-5, and finally 4-5.There could be a diode shorted as well which would require each test to be done with the leads reversed just to see if the resistance changes, then we know we have a diode action going on...could be a transistor as well. Still don't know what we would do with it, but just maybe..... Your problem shows that the newer design is no better than the OEM! Damn, had hoped it would be better as the quill layout is better for heat sink action.

not that bad of a right up... its never that ez.. but this is the steps...
of course 200% of this fourm doesnt understand what the frakk that means... but at least its here

Originally Posted by Burning2nd

200% of this fourm doesnt understand ... but at least its here

Speaking of understanding parasitic drain diagnostic procedures, EdJack recommended this thread over here today:

Originally Posted by edjack

bluebee, you may wish to reference this PDF http://www.bimmerfest.com/forums/sho...d.php?t=683264

Looks like a superior way to find current drains, if you have a sensitive enough DMM, and the skill to make accurate measurements..

Due to the state of the CAN Bus communications in the vehicle, it is no longer acceptable to pull each individual fuse one at a time to try and identify which circuit is consuming current. Removal/ reinsertion of a fuse while vehicle is in a sleep state may wake the bus of the vehicle, and invalidate the test. Identifying "consuming" circuits must be done by measuring a voltage drop across fuse and aligning with the value in matrix located at end of this document.

The reference document is located here:
- vw.tb.27-07-11 Battery Discharged Diagnosis for Static Current Draw.pdf (111.9 KB)

It's not all that easy to understand their recommended method:

1. Connect calibrated 50 amp current clamp to the battery negative cable
2. Close all doors, trunk, or hood latch so vehicle control units detect all doors closed
3. Arm vehicle anti-theft system with remote
4. Observe sleep state current draw after vehicle is left untouched for TWO HOURS.
5. If after two hours the vehicle does not exceed maximum sleep state current draw, perform a long term (overnight) measurement test

If the parasitic current is too high in the above tests, then run the following Consuming Circuit Isolation test:

1. Measure the millivolt drop across the resting fuse (e.g., 0.3mv)
2. Given the fuse amperage (e.g., 5A), check what current draw that equates to (e.g., 20ma)
3. Now you know the resting current through that fuse is 20 milliamps