Hello there and welcome to the BMW Car Club of America.

If you are a BMW CCA member, please log in and introduce yourself in our Member Introductions section.

528iT battery goes dead

Discussion in 'E39 (1997-2003)' started by aggardner, Oct 26, 2008.

    aggardner guest

    Post Count: 4
    Likes Received:0
    My 2000 528iT battery goes dead if the car sits for more than a day or two. The battery is new and checks out. Nothing seems to be staying on, the consol shifter light goes out as it should, but when I connect a battery charger it appears there is a load on the circuit. Any suggestions?

    BMWguy206 guest

    Post Count: 43
    Likes Received:0
    What kind of battery and size did you get?

    It's very common though that the final stage resistor unit for the AC/Heater blower will remain on the lowest setting. So sometimes when you shut off the car and turn the blower off on the AC control, the final stage resistor will still be powered up and spinning the blower at a very low speed.

    aggardner guest

    Post Count: 4
    Likes Received:0
    I had my local BMW mechanic replace the battery with an aftermarket spec battery. The blower motor makes sense, would I be able to detect it running? Any idea on what component would have failed?

    BMWguy206 guest

    Post Count: 43
    Likes Received:0
    Yes you should be able to but it'll be intermitent. When the vehicle is off put your hand or face on the center vents and if you feel a bit of air coming out of it, then the blower is spinning because the final stage resistor unit is the cause.

    The final stage blower resisitor unit is on the evaporator box and you can access it from the passenger side footwell area.

    If it's not the final stage resistor unit then it can be any control unit remaining on and those can take some time to diagnose.

    Are you having any blower issues at all while driving like blower will be erratic?

    aggardner guest

    Post Count: 4
    Likes Received:0
    I'd hadn't picked up on anything erratic from the blower. I'm wondering if I were to pull the fuse and let it sit a day or two to see if the battery runs down would narrow it down?

    BMWguy206 guest

    Post Count: 43
    Likes Received:0
    Yes that's probably the easiest thing to do.
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    Just to be clear, if you pull the blower motor fuse, the blower final stage may still try to power up and may cause the battery to drain, but much slower than before, since there will be no load. If you pull the IHKA (climate control) fuse and the blower fuse and the battery still dies, you have ruled that out. That said, the blower final stage is the single most common cause of battery drain on these cars. You may only notice it if you happen to be sitting in the car and hear the blower come on even when it is not powered up. Very difficult to catch. The updated part is much better and I have yet to see one fail.

    aggardner guest

    Post Count: 4
    Likes Received:0
    I've determined that (after hooking up an ammeter) after everything has shut down there is still over 1 amp of current flowing continuously. Now the problem I face is there is no fuse diagram in the owners manual, so which fuse controls what? Any suggestions on where to find that information?
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    How long do you wait? The car make take up to 30 minutes to "go to sleep" and you absolutely cannot disturb anything in the car at that point. You can't open the doors, bump it, move the key, etc. Only then can you get the true at rest current draw. Once you find the fuse, post it and someone with access to the ETM can look to see what circuits are active.

Share This Page