2002 528i dead battery problem please help!! - BMW Forum

mbaconusa · 01-28-2010, 08:06 AM

I have a 2002 528i cold weather package (heated mirrors, seats, stearing wheel and jet sprayers) and my battery seams to be acting wierd alot of the time. I had the alternator and battery checked and both of them are good. I dont arm my alarm anymore because it usually goes off in the middle of the night for no reason. sometimes when i go to start the car in themorning after it sat all night is starts with no problem, sometimes it doesnt. I keep a jump pack in mytrunk and i usually have to jump it quite frequently. sometimes i will go to leave in the morning and there is only 6 volts or less in the battery. something is deffintetly draining the battery but not all the time. my outside thermostat is diconnected would this cause the heated mirrors to sometimes come on? this is so frustrating. sometimes the car will start fine and then ill go right down the road and when i go to start the car its dead just clicking. any help is appreciated

wayne adesso · 02-01-2010, 12:16 AM

Hi,check your fsu (final stage unit ) might just be your problem, there are DIYs for this,
check it out and good luck,Hope it helps.

mbaconusa · 02-07-2010, 01:01 PM

thanks! i replaced the FSU and the battery hasnt died on me in over a week!!! its finally back to normal! just to add the FSU went out right around 80k miles. for other people who might have the same problem

wayne adesso · 02-08-2010, 08:56 PM

Your welcome buddy, its nice to see it worked out for ya.

Raymond Lee · 02-23-2010, 06:58 PM

wayne adesso
A nice story here! It is not my car but I am glad of the story! A problem like that can be very tricky and costly!

shutchomatic · 03-11-2010, 05:44 PM

Wayne,
I have a 2000 528i E39
Found all the postings about the FSU and have since replaced it; however, I still hear the fan noise coming from behind the AC Control Unit and if I leave the car sitting for too long the battery gets low.
Is there anything else (other than a DOA FSU) that you can suggest?
Thank You

wayne adesso · 03-13-2010, 09:00 PM

shutcromatic,
I wish I had a good answer for you,I guess it could be possible the FSU is defective or not making a good connection, sometimes the pins on a connector can bend out of wack.The car should go to sleep when its turned off,have you added any after market components or altered the wiring in any way? These cars are so packed with electrical components its really hard to find the problems.
Maybe try pulling up the wiring diagram and see just what else is on the same circuit, maybe something will jump right out at you. look at the REST feature, its the only thing I can think of that works with the key off other than the alarm.
Sorry I don't have a solid answer for you, keep us all posted on what you find cause it really helps all of us understand our Bimmers better. Good Luck!!!

wayne adesso · 03-14-2010, 02:14 PM

shutchromatic, Have some additional information for you, found another thread with similar symptoms as yours. Replaced FSU still had battery drain. The solution was a resister in the blower motor, try tracking that component down,Hope that helps.