W202 alarm

Discussion in 'Electronics' started by cuprastu, Oct 16, 2011.

  1. cuprastu

    cuprastu Member

    Messages:
    38
    Joined:
    Sep 25, 2009
    Location:
    Herts
    Car:
    W202 230K Sport
    I have a problem with the alarm on my car, it is a facelift 202 and will randomly go off, so have resorted to turning off the interior sensors everytime I park it at night, mostly this is ok. However the other day I noticed that the indicators on it were flashing really fast but no siren going off, once I unlocked it it was ok again.

    Is there anything I can check, or a battery in the alarm i can replace that might sort this out? The cars main battery was changed last winter so don't think it's a battery voltage issue.
     
  2. gchild

    gchild Active Member

    Messages:
    507
    Joined:
    Apr 21, 2004
    Car:
    C280 Sport
    I had a similar issue. Turned out to be a cricket that got in some how triggering the interior sensor. Took a few weeks for it to surface, had the interios sensor off in the meantime
     
  3. OP
    OP
    cuprastu

    cuprastu Member

    Messages:
    38
    Joined:
    Sep 25, 2009
    Location:
    Herts
    Car:
    W202 230K Sport
    Mine has been doing it ever since I have had the car, which is over 2 years now so anything living should be well dead! It's just annoying and seems to be getting getting worse. It's the rapid flashing of the indicators the other day that started me worrying about it more.
     
  4. horgantrevor

    horgantrevor MB Enthusiast

    Messages:
    1,902
    Joined:
    Jan 14, 2011
    Car:
    w202 c43 & w210 E220 CDI estate w219 W221
    hi get the car tested on a star system

    also check the wiring to the siren and check for bad earths
     
  5. OP
    OP
    cuprastu

    cuprastu Member

    Messages:
    38
    Joined:
    Sep 25, 2009
    Location:
    Herts
    Car:
    W202 230K Sport
    Never thought about checking for bad earths, that's the quickest and cheapest option to explore first!

    Thanks
     
  6. horgantrevor

    horgantrevor MB Enthusiast

    Messages:
    1,902
    Joined:
    Jan 14, 2011
    Car:
    w202 c43 & w210 E220 CDI estate w219 W221
    earth wire is brown
     
  7. Justin1600

    Justin1600 MB Enthusiast

    Messages:
    2,079
    Joined:
    Dec 28, 2010
    Car:
    C43 AMG
    Try cleaning the interior sensors on the B pillars first, if that still does not cure it then the chances are the PSE pump is at fault.
    But as said above check the wiring to the Siren for corrosion :thumb:
     
  8. OP
    OP
    cuprastu

    cuprastu Member

    Messages:
    38
    Joined:
    Sep 25, 2009
    Location:
    Herts
    Car:
    W202 230K Sport
    What's the PSE pump, is that what operates the central locking etc? If so that is all fine.
     
  9. Justin1600

    Justin1600 MB Enthusiast

    Messages:
    2,079
    Joined:
    Dec 28, 2010
    Car:
    C43 AMG

    Yes mate, it is in the boot on the drivers side. Do the things i said first, if it still goes off then you will need to do a Star short test. If there are lots of fault codes stored in PSE which say Left protection senor & Right protection sensor, then the PSE pump will probably be faulty :thumb:

    The central locking etc will still work mate
     
  10. OP
    OP
    cuprastu

    cuprastu Member

    Messages:
    38
    Joined:
    Sep 25, 2009
    Location:
    Herts
    Car:
    W202 230K Sport
    Lovely stuff, thanks for your help!
     
  11. andy27168

    andy27168 MB Enthusiast

    Messages:
    4,407
    Joined:
    Nov 27, 2004
    Location:
    Southampton
    Car:
    1997 C230K, 1999 C43/55 AMG
    False alarms like this (once false alarms have been eliminated) are most likely caused by a faulty alarm siren, the back up battery in the siren gives up causing the issue, I had this exact issue with my C43.
     
    1 person likes this.
  12. Alex Crow

    Alex Crow Active Member

    Messages:
    278
    Joined:
    Sep 30, 2011
    Location:
    Super Suffolk
    Car:
    S210 320cdi
    Andy above has it right, if the alarm goes off without the siren (indicators flashing), it is usually the siren at fault.

    This will be mounted in front of the N/S/F wheel, and can be disconnected to prove the fault.
     
    1 person likes this.
  13. andy27168

    andy27168 MB Enthusiast

    Messages:
    4,407
    Joined:
    Nov 27, 2004
    Location:
    Southampton
    Car:
    1997 C230K, 1999 C43/55 AMG
    Hi,
    The Siren battery cannot be replaced, you have to replace the entire Siren, approx. £75 from MB only.
    You will need a T30 security Torx bit to remove it from the car.
     
  14. OP
    OP
    cuprastu

    cuprastu Member

    Messages:
    38
    Joined:
    Sep 25, 2009
    Location:
    Herts
    Car:
    W202 230K Sport
    This is all sounding expensive! What would happen if I just disconnected the siren?
     
  15. Alex Crow

    Alex Crow Active Member

    Messages:
    278
    Joined:
    Sep 30, 2011
    Location:
    Super Suffolk
    Car:
    S210 320cdi
    As before, I recommend this to prove the fault.

    The car will be quite happy without it.
     
  16. OP
    OP
    cuprastu

    cuprastu Member

    Messages:
    38
    Joined:
    Sep 25, 2009
    Location:
    Herts
    Car:
    W202 230K Sport
    Well if it fixes the fault I might just leave it permanently disconnected. Don't need a poxy alarm anyway, no one takes any notice of them!

    Thanks for your help.
     
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