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Thread: In need of some advice on an electrical issue...

  1. #1
    Join Date
    Dec 2013
    Location
    Kingston, ny, USA
    Posts
    8
    My Cars
    2003 BMW Z4

    In need of some advice on an electrical issue...

    Collective expert minds,

    I have a 2003 2.5L Z4. Up to now, running pretty well, normal maintenance and Wear and tear

    The car was running on Monday, no issues, no lights

    Today, I went to unlock and it would not unlock. I manually unlocked and discovered the car was dead as a doornail. No light, no clicks. Autoranging meter reading on battery showed a tiny voltage (something > 1mV)

    My wife came home and we tried to jump start it. At the very first, the dash came alive but it would not turn over. We waited a bit and when I put in the key, no lights again.

    Voltage from cables when not connected to my car is something like 13.6V (in other words, my wife's car is putting out enough)

    Voltage reading on posts, when connected via jumpers, is something like .5V

    Does this mean perhaps a fuse blew? Clearly, something is not right.
    I could try hooking to the battery in the trunk but I've heard that can mess up your electronics.

    BTW, I know my way around a wrench, but for the electronics, it gets beyond me.

    Thoughts, advice, other things to check/try? More information needed? What info can I glean from these meter readings besides my conclusion that "it's broken"?

    Frustrated in NYS...

    Help me Bimmerforum Kenobis...you are my only hope! ;-)

    Tom

  2. #2
    Join Date
    Oct 2012
    Location
    Victoria BC Canada
    Posts
    380
    My Cars
    2004 Z4, 1700 Nomad MC
    Remove and test battery sounds like it’s dead and needs replacement.

    Yes... battery can work one day and next day be dead as a door nail. I’ve had two cars die on me that way over the years. Replaced my Z4 battery when I got it and use a battery maintainer (CTEC) any time it’s not being used. 5 1/2 years and it’s still going strong.


    Sent from my iPhone using Tapatalk

  3. #3
    Join Date
    Jan 2015
    Location
    Timaru, New Zealand
    Posts
    1,132
    My Cars
    Two Z3 Roadsters
    If you are testing the voltage at the battery terminals and getting >1mV, I would suggest that your battery has died over night and needs replacement.
    1999 2.8L Z3 Roadster,
    2000 3.0L Z3 Roadster,

    There is only one thing more pleasurable than working on a Z3, that's driving it top down on a fine day.

  4. #4
    Join Date
    Dec 2013
    Location
    Chicagoland area
    Posts
    4,372
    My Cars
    EXOTICS
    How old is this battery? AVG lifespan is about 5yrs.
    Under no circumstances should you attempt to jumpstart a DEAD battery.
    Bad for vehicles electrical system on either end of cables.

  5. #5
    Join Date
    Dec 2013
    Location
    Kingston, ny, USA
    Posts
    8
    My Cars
    2003 BMW Z4
    So this battery was less than 18 months old.

    I brought it back to Advance Auto which replaced it under warranty

    Car started right up, ran fine. The voltage across the battery while running was 13.7 or so volts, which seems indicates alternator is functioning.

    Today, went to start it, clicks won't start, so battery not totally dead.

    It seems that something is draining this battery, and I have nothing plugged in anywhere. Aside from this, no obvious issues.
    If not for the fact that the idiot battery light turns on with the rest of the dash lights when I start the car, I'd suspect that the bulb was burned out and so I'd not be aware of an ongoing issue.

    *edit* on the advice of a friend, I am checking to make sure glovebox/trunk lights are not stuck on somehow.
    Last edited by THChess; 04-02-2019 at 03:06 PM.

  6. #6
    Join Date
    Jan 2015
    Location
    Timaru, New Zealand
    Posts
    1,132
    My Cars
    Two Z3 Roadsters
    Time to recharge the battery and start testing for the draining load.

    Set up a multi meter in series with the battery, either on the positive or negative post, which ever is easiest. Have the multi meter on DC Current (A). Start pulling fuses one by one until the current does a big drop. Investigate what ever that fuse controls.
    1999 2.8L Z3 Roadster,
    2000 3.0L Z3 Roadster,

    There is only one thing more pleasurable than working on a Z3, that's driving it top down on a fine day.

  7. #7
    Join Date
    Dec 2013
    Location
    Kingston, ny, USA
    Posts
    8
    My Cars
    2003 BMW Z4
    Quote Originally Posted by Muzz258 View Post
    Time to recharge the battery and start testing for the draining load.

    Set up a multimeter in series with the battery, either on the positive or negative post, which ever is easiest. Have the ulti meter on DC Current (A). Start pulling fuses one by one until the current does a big drop. Investigate whatever that fuse controls.

    The battery is now out of the car, and will charge overnight. We'll see how it goes in the AM.

    In theory, with the car off, there should be no drain at all on the battery, right? Obviously, there will be a drain somewhere, so this is a good (but tedious) thing to try (check, pull, check again, pull, etc) Thank you!

    I bought a device today for a few bucks that hooks to the battery terminals and sends an alert if the battery drops below a set point. Once I get the car running again, I will check that out.

  8. #8
    Join Date
    Dec 2013
    Location
    Chicagoland area
    Posts
    4,372
    My Cars
    EXOTICS
    Test for parasitic drain.
    Many examples on YouTube.

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