Results 1 to 10 of 10

Thread: weird electrical issue

  1. #1
    Join Date
    Feb 2016
    Location
    Austin TX
    Posts
    19
    My Cars
    91 e30, 02 540iT, 06 550

    weird electrical issue

    2002 540i. Was running fine for the last week, recent changes were new SLS air pump, oil change and brake fluid flush. this happened about 3 days after the fluids.

    Went to inlaws' house, when leaving I went to start the car and heard a slight bang (could have been the starter engaging). Now when the key is in any position besides off, some of the dash lights flash rapidly and you can hear a few relays going. When you turn the key back off, the interior lights slowly pulse off and on, like on a 5 second cycle.

    Starting to pull fuses and check them now...with the weird light thing I am wondering if a module died....

    battery is showing 12.3v, even tried with a nice plug in jumper/charger.

    I've been getting teh battery light flickering for a while, I assumed the alternator was on its way out.

  2. #2
    Join Date
    Oct 2016
    Location
    toronto
    Posts
    126
    My Cars
    540
    check the trunk wiring harness? but fuses should be blowing in that case... flickering battery light may also be your oil level sensor. They are on the same circuit in my 97 540.

  3. #3
    Join Date
    Feb 2016
    Location
    Austin TX
    Posts
    19
    My Cars
    91 e30, 02 540iT, 06 550
    LOL ended up being battery. I guess it would hold a charge but couldn't put out any amps? I couldn't even jump the car. New battery and everything is working 100%. Alt seems to be putting out good voltage still too. Just an update for someone googling this issue 5 years from now...

  4. #4
    Join Date
    Oct 2010
    Location
    San Jose, CA
    Posts
    11,537
    My Cars
    1997 BMW 540i 6 speed
    Thanks for the feedback. 12.3 V indicates that the battery is only 50% charged. The plates were probably sulfated, so it could not deliver much current. Once the battery is sulfated, it becomes non-serviceable, and should be replaced.
    Last edited by edjack; 07-12-2020 at 07:49 PM.


    Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.

  5. #5
    Join Date
    Jul 2017
    Location
    Turkey
    Posts
    839
    My Cars
    '00 540i M-Tech
    Quote Originally Posted by edjack View Post
    Once the battery is sulfated, it becomes non-serviceable, and should be replaced.
    wrong...

    adding water and applying a higher than normal voltage (15-16v) for several hours to a sulfated battery usually revives it.

    a heavily hard sulfated battery is another story... they are usually non revivable.

  6. #6
    Join Date
    Feb 2014
    Location
    Alexandria, VA
    Posts
    9,049
    My Cars
    ‘01 540’00 528T’03 525T
    Quote Originally Posted by TiesTorN View Post
    wrong...

    adding water and applying a higher than normal voltage (15-16v) for several hours to a sulfated battery usually revives it.

    a heavily hard sulfated battery is another story... they are usually non revivable.
    Wrong..... you desulfate a sulfated battery with a capable slow charger, usually takes 48 hours or more. Best way is to drain some of the old acid out, refill with distilled water and the slow charge breaks up the sulfur build up off of the cells, hence, desulfation of the cells. You don’t hit it with high Voltages.
    Set the controls for the heart of the sun

  7. #7
    Join Date
    Jul 2017
    Location
    Turkey
    Posts
    839
    My Cars
    '00 540i M-Tech
    Quote Originally Posted by BimmrMeUpSnotty View Post
    Wrong..... you desulfate a sulfated battery with a capable slow charger, usually takes 48 hours or more. Best way is to drain some of the old acid out, refill with distilled water and the slow charge breaks up the sulfur build up off of the cells, hence, desulfation of the cells. You don’t hit it with high Voltages.
    yes u need to do it slow but slow means low ampere, not low voltage. you need to use a charger that can charge with higher voltage. this process is also called as equalization process.

    https://batteryuniversity.com/learn/...alizing_charge
    Last edited by TiesTorN; 07-14-2020 at 09:53 AM.

  8. #8
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
    Join Date
    Oct 2006
    Location
    Sundance Mesa, NM
    Posts
    19,817
    My Cars
    00 540/6, '16 Highlander
    ^_almost nobody here has a charger that will do that.
    A good smart charger is all you need to desulfate the lead plates.

  9. #9
    Join Date
    Jul 2017
    Location
    Turkey
    Posts
    839
    My Cars
    '00 540i M-Tech
    Quote Originally Posted by JimLev View Post
    A good smart charger is all you need to desulfate the lead plates.
    sigh... whatever. you guys keep repeating yourselves and don't learn. I even shared a link with you so u can read but... anyway cya.

  10. #10
    Join Date
    Feb 2014
    Location
    Alexandria, VA
    Posts
    9,049
    My Cars
    ‘01 540’00 528T’03 525T
    Sigh, didn’t need to read it, my slow Genius chargers all do it, and do it well.
    Set the controls for the heart of the sun

Similar Threads

  1. Weird electrical issue, gauges die while driving
    By tylerboze in forum 1991 - 1999 (E36)
    Replies: 5
    Last Post: 11-21-2009, 04:02 PM
  2. Weird electrical issues (1988 BMW 735i)
    By SeanH in forum 1988 - 1994 (E32)
    Replies: 14
    Last Post: 09-07-2009, 09:13 AM
  3. Replies: 0
    Last Post: 12-16-2008, 11:07 PM
  4. Weird electrical issues
    By Rosster in forum General BMW and Automotive Discussion sponsored by Intercity Lines
    Replies: 0
    Last Post: 04-19-2008, 08:26 AM
  5. Weird Electrical Issues - 2003 325i
    By petieg383 in forum 1999 - 2006 (E46)
    Replies: 5
    Last Post: 08-27-2007, 09:58 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •