FSU - Battery Drain

My A/C fan has been acting erratically and yesterday found out my battery is drained. Had to jump it. I know that there are alot of threads regarding FSU but I want to know if there is something I can do to prevent battery drain for temp solution until I get the new FSU. I just unplug the battery after I parked today. Thanks...

Unplug the FSU. But, no A/C then. How long does it take to stop by the dealer and pick up a new FSU? ebaY units are not reliable, and you'll be wasting your money.

"unplug the battery?" How you do that?

Originally Posted by edjack

Unplug the FSU. But, no A/C then. How long does it take to stop by the dealer and pick up a new FSU? ebaY units are not reliable, and you'll be wasting your money.

"unplug the battery?" How you do that?

I leave to work by 7AM and do not get home until 10PM so no way I can stop by the dealer.

So I should not think about ordering a used OEM one from ebay?

"unplug the battery" = remove the negative cable...sorry, didnt use the correct term

Suit yourself.

Originally Posted by ill_kuma

I leave to work by 7AM and do not get home until 10PM so no way I can stop by the dealer.

So I should not think about ordering a used OEM one from ebay?

"unplug the battery" = remove the negative cable...sorry, didnt use the correct term

for a small charge. NOT not from EBAY,

Just ordered from BMW dealer today. In the meanwhile, I will have to unplug/disconnect/remove the negative cable each time I park my car for a long period of time (morning and night).

Originally Posted by ill_kuma

Just ordered from BMW dealer today. In the meanwhile, I will have to unplug/disconnect/remove the negative cable each time I park my car for a long period of time (morning and night).

You should buy one of these and just unscrew the knob. Saves the pain of hazard of constantly removing the negative cable.

http://www.amazon.com/Post-Battery-M.../dp/B001N729FS

Bets $8 I spent in a while.

Ok, I replaced the FSU and blower is running normal now BUT still woke up this morning to a dead battery. What next? Check battery if its holds charge?

Measure the battery sleep current (wait 20 minutes after turning off the ignition) and start removing the fuses. Sleep current shouldn't exceed 50mA.

Sent from my ADR6350 using Bimmer App

Originally Posted by acoste

Measure the battery sleep current (wait 20 minutes after turning off the ignition) and start removing the fuses. Sleep current shouldn't exceed 50mA.

Sent from my ADR6350 using Bimmer App

So should I wait 20 mins after I open the trunk as well or can I do this right after the trunk light goes off?

After the trunk light goes off = 16 min.

Where did you get the FSU? Did it have 39 spikes on the heat sink?

Originally Posted by edjack

After the trunk light goes off = 16 min.

Where did you get the FSU? Did it have 39 spikes on the heat sink?

I ordered the OEM FSU from a dealer. Its has the 39 spikes.

Ok, this is what I have done so far.
Started reading at 3.53Amp.
Removed fuse #4 to disable the interior/trunk/glove compartment lights.
Reading at 1.50 - 1.53 after removing fuse #4.

For References:
#7 = Cigarette Lighter
#12 = Immobilizer (What is this?)
#13 = Driver Seat Adjustment
#22 = Auxiliary Fan
#31 = ABS (My ABS light is on in dashboard - light came on after getting car back from shop for the fuel pump wire issue)
#56 = On-Board Monitor / Radio (I have a DICE unit that is routed from the trunk)

Troubleshooting Begins:
Removed #7 and it dropped to .80
Plugged back in and it stayed on .80 until I re-read with the multimeter again then back to 1.51.

Removed #12 and it dropped to .81
Plugged back in and reading is back to 1.51

Removed #13 and it dropped to .81
Plugged back in and it stayed on .80 until I re-read with the multimeter again then back to 1.51.

Removed #22 and it dropped to .81
Plugged back in and reading is back to 1.51 (saw sparks when plugging back in)

Removed #31 and it dropped to 1.40
Plugged back in and reading is back to 1.51

Removed #31 and it dropped to .80
Plugged back in and reading is back to 1.50

After removing fuses # 7, 12, 13, 22, 31, 56 the reading is at .09-.10.

Any advice / ideas?

I also had this issue.

Unplug power from the DICE unit.

Let the car go to sleep. What do you see?

Originally Posted by pleiades

Unplug power from the DICE unit.

Let the car go to sleep. What do you see?

So try the procedures again with the DICE unit unplugged?

Originally Posted by ill_kuma

So try the procedures again with the DICE unit unplugged?

yes

Originally Posted by pleiades

yes

Too dark outside now and no garage. Will have to wait until next weekend. At the meantime, I guess I will unplug DICE unit. Is there anything else I can unplug (like fuses) to save my battery?

Originally Posted by ill_kuma

Too dark outside now and no garage. Will have to wait until next weekend. At the meantime, I guess I will unplug DICE unit. Is there anything else I can unplug (like fuses) to save my battery?

Probably but I would not be surprised if the DICE is your parasite.

You could install a disconnect switch like dvsgene recommended. You may be able to find one locally at an automotive store or walmart.

And you might want to run the car and do test #9 on the instrument cluster to measure your alternator's health.

So fuse #22 is the Aux Fan. I removed the fuse #22 and left the car there for 5 days without starting it up. Then I put back the fuse #22 and it started up with no problem. It is safe to say that this is related to the Aux Fan. I read that some E39's Aux Fan will turn on or stay on after the car shuts off. In my case, the fan shuts off and does not start up by itself...only thing is its constantly draining the battery.

Where should I go from here?

It's most likely the aux fan controller that is going bad. You get erratic operation of th aux fan; sometimes it doesn't start when the A/C is engaged; it may also run after ignition is switched off. A friend had a similar problem with his aux fan on an e46 (same construction) and the controller shorted out and caught on fire.

I have had a battery drain issue as well, it will be fine for weeks sometimes, other times it will be mere days between flat battery episodes... I do hear a fan going inside the A/C unit from time to time after the car is shut off, sometimes hours afterwards.
I will investigate this Aux Fan as to being the possible culprit. This will be a huge worry off my mind because it's nerve racking not knowing when the dreaded 'click-tick-tick-tick' will strike... it can happen anywhere at any time.