1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

key recognition problem?

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by MarkyBoy, Nov 28, 2012.

  1. MarkyBoy

    MarkyBoy Senior Member

    Messages:
    84
    Likes Received:
    0
    Joined:
    Sep 8, 2009
    Hi all, wonder if anyone can help isolate a starting problem with a 1998 C250TD.

    The problem started about 6 weeks ago, when turning the ignition key the engine just goes 'clunk' it doesn't attempt to turn over, you try a few times and the engine just clunks repeatedly, then after a few attempts it will turn over without starting. Then if you remove the key and try again it will start normally. After a week or so, I switched to the spare key and the problem disappeared. BUT after a couple of weeks the problem exists with the spare key now as well and is worse than ever!

    I have checked the battery and had the starter motor tested and all is ok with those, so I wonder if the problem is that the key is not being 'recognised' or something... The batteries in the keys are only a couple of years old, but perhaps that's an issue? Any ideas how I can diagnose and isolate what the problem is?
     
  2. grahamcol

    grahamcol Senior Member

    Messages:
    1,462
    Likes Received:
    322
    Joined:
    Jan 12, 2009
    Location:
    West Midlands
    Your Mercedes:
    2001 SLK230, 2007 CLK220 CDI
    Batteries are only "a couple of years old" suggests they mau need replacements. Worth a try. However, I'm not certain this will be the root cause of the problem. I would say that after a couple of years the batteries are very likely well past their best. Good luck
     
  3. OP
    MarkyBoy

    MarkyBoy Senior Member

    Messages:
    84
    Likes Received:
    0
    Joined:
    Sep 8, 2009
    Don't know if this is connected or not, but the windows do not 'latch' on the switches until the car is running (and key is recognised?) after which they will work fine???!!
     
  4. drmw

    drmw Moderator

    Messages:
    3,681
    Likes Received:
    112
    Joined:
    Nov 25, 2007
    Location:
    Yorkshire
    Your Mercedes:
    M6 Cab - prior to that, SL63 AMG, A-M V8 Vantage, SL55, SL500 and many more
    for the sake of a fiver, I would change the batteries - 2 years isn't too bad depending on use.
     
  5. OP
    MarkyBoy

    MarkyBoy Senior Member

    Messages:
    84
    Likes Received:
    0
    Joined:
    Sep 8, 2009

    Yes, I'm going to get some batteries tomorrow but would they really cause this kind of problems? I just read you could start the car without any batteries in the key?
     
  6. Mark@RMK

    Mark@RMK Senior Member Authorised Forum Supporter

    Messages:
    534
    Likes Received:
    8
    Joined:
    Jan 4, 2010
    Location:
    Birmingham
    Your Mercedes:
    115CDi Vito
    Batteries only work the locking part of the key..

    It could be the keys but if they turn and the start clunks then all the authorisations are being given by the EIS/ECU to start.
     

Share This Page