Large Parasitic Draw on Battery

Discussion in 'Electronics' started by Voyager, Feb 8, 2014.

  1. Voyager

    Voyager Active Member

    Messages:
    123
    Joined:
    Oct 31, 2008
    Hi
    My car is a 2001 S210 E320 cdi estate

    Last week the garage diagnosed a large 18Amp draw on the battery when the car was shut down and after tess concluded it was the Alternator.

    The Alternator was replaced and the car was picked up at 6pm yesterday. At 9pm yesterday the alarm went off; when I went out to investigate, the battery was dead. Something is still drawing charge when car is shut-down and locked??

    100% sure no doors, windows of lights had been left on.

    Does anyone have an idea what could be wrong please ? (The battery is only 8 weeks old and alternator is new).:wallbash:

    thanks......
     
  2. jaymanek

    jaymanek Authorised Forum Sponsor Authorised Forum Sponsor

    Messages:
    16,412
    Joined:
    Nov 29, 2002
    Location:
    Nuneaton Warwickshire
    Car:
    Lots of Mercedes!
    It could be one of many things.

    The only way to do it is to place an ammeter in series at battery and pull fuses until you see current draw drop.. Any decent garage can do this.
     
    1 person likes this.
  3. jamesfuller

    jamesfuller MB Enthusiast

    Messages:
    1,171
    Joined:
    Aug 14, 2013
    Location:
    Northamptonshire
    Car:
    The one that starts!
    Its not usually difficult to find a draw, just time consuming. Are you going to look into it yourself or take it back to the the garage?
     
    1 person likes this.
  4. Sp!ke

    Sp!ke Administrator

    Messages:
    12,234
    Joined:
    Jun 2, 2002
    Location:
    West London
    Car:
    SL500 & The Fart Car
    This sort of thing is best left to a vehicle electrical specialist or you could be chasing your tail for a while.

    If you have a decent multimeter and some electrical know how you could remove the fuses one by one whilst measuring the current draw on the battery (with everything off and the doors shut).

    This would pinpoint which circuit the problem lies, allowing you to investigate further.

    18 amps is huge...
     
    1 person likes this.
  5. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

    Messages:
    18,922
    Joined:
    Feb 8, 2007
    Location:
    Portsmouth, Hampshire.
    Car:
    E55K SL500 E300Hybrid E250X3 Viano C55 E450Cab A180 Smart 44 Brabus
    I expect it to be a preheater of some kind with that kind of draw.

    No need for a electrical specialist. Any decent MB independent can do it.
     
  6. OP
    OP
    Voyager

    Voyager Active Member

    Messages:
    123
    Joined:
    Oct 31, 2008
    yes, the garage did check all the fuses and non were faulty. was just the alternator that was drawing power - hence the replacement........but must be something else - or something intermittent.........?
     
  7. OP
    OP
    Voyager

    Voyager Active Member

    Messages:
    123
    Joined:
    Oct 31, 2008
    yes, agree - must have a heating element to draw that amount.
     
  8. Ted

    Ted MB Enthusiast

    Messages:
    5,758
    Joined:
    Feb 26, 2004
    Location:
    Bourton on Dunsmore
    Car:
    SLC 250D AMG Line, Yamaha XVS 1100, Jeep Renegade
    At well over 200 watts something is getting pretty hot. Shouldn't be too hard to find.
     
  9. V12

    V12 MB Enthusiast

    Messages:
    5,610
    Joined:
    Jun 17, 2002
    Location:
    Southampton
    Car:
    S320CDI LWB
    Open the bonnet and look to your left hand side, you'll see 2 black tank looking things.
    From memory, furthest to the left is water expansion tank for radiator and the other is the electric booster heater. I'm pretty sure this is fed power directly from the alternator point but seeing as it is basically a kettle element and that it draws it's power from the alternator point it would be my first port.
    Unplug it and see what happens.

    I replaced the unit on my W210 320cdi, it was an easy swap. Mine wasn't draining the battery but was completely dead.
     
    1 person likes this.
  10. OP
    OP
    Voyager

    Voyager Active Member

    Messages:
    123
    Joined:
    Oct 31, 2008
    take it back to the garage
     
  11. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

    Messages:
    18,922
    Joined:
    Feb 8, 2007
    Location:
    Portsmouth, Hampshire.
    Car:
    E55K SL500 E300Hybrid E250X3 Viano C55 E450Cab A180 Smart 44 Brabus
    The alternator will never cause a current draw. Why did they replace that!

    Go somewhere else.
     
  12. moonloops

    moonloops MB Enthusiast

    Messages:
    5,312
    Joined:
    Oct 8, 2009
    Location:
    :Location : Location
    Car:
    W204 C350 CDI AMG Sport


    ^^This^^

    Best advice, same as I followed a while back and easily found the culprit.
     
  13. jaymanek

    jaymanek Authorised Forum Sponsor Authorised Forum Sponsor

    Messages:
    16,412
    Joined:
    Nov 29, 2002
    Location:
    Nuneaton Warwickshire
    Car:
    Lots of Mercedes!
    The alternator may not have been charging properly? Those water cooled alternators do commonly fail.
     
  14. grober

    grober MB Master

    Messages:
    27,913
    Joined:
    Jun 22, 2003
    Location:
    Perth, Scotland
    Car:
    W204 C200CDI Estate
    Have you got heated seats?
     
  15. Deadly Dave

    Deadly Dave Active Member

    Messages:
    279
    Joined:
    Oct 16, 2010
    Location:
    Dublin, Ireland
    Car:
    1988 300CE & 1965 230SL
    It will if diodes fail in the regulator.
     
    1 person likes this.
  16. brucemillar

    brucemillar MB Enthusiast

    Messages:
    8,663
    Joined:
    Nov 18, 2010
    Location:
    Next Door to Alice - 25 'kin years now
    Car:
    C55 AMG Wagon - W124 300te 4matic Wagon - BMW 4.8is X5 E53 - SWB Pajero 3.5 V6 24v
    and.. If you alternator was toast? Whatever is causing this draw maybe about to toast your new alternator.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.