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All electrics shut down when turning key

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by Hustler, Nov 10, 2018 at 2:42 PM.

  1. Hustler

    Hustler Senior Member

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    Joined:
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    Location:
    United Kingdom
    Your Mercedes:
    2003 C200 Kompressor Coupe 1.8L
    Hi guys,

    For the last few years I've had an intermittent problem and would be extremely grateful if anyone can offer some help.

    Issue:

    When I insert the key into the ignition and turn the key to start all the electrics would completely cut out - no display on the dash - electric windows, central locking - basically the entire car with no electrics as though the battery had been disconnected. Position 1 and 2 on the key are fine, it's usually the final turn of the key to start when you would here the tick sound and then all electrics shut down immediately.

    An example of the issue can be seen here:



    It would sometimes (but rarely) occur when I press the unlock button on the key fob.

    Last night, for the very first time, I was driving and the ESP warning on dash appeared and the stereo shut out for a brief second before immediately starting back up. Managed to drive for 5 more mins and parked up. As soon as I took the key out, all electrics cut off.


    Other info:

    Whenever this happens, I normally flip open the bonnet and disconnect the ground cable from the negative terminal on the battery. Wait a couple of seconds and then reconnect.

    Car starts up perfectly normal. (Sometimes I need to disconnect and re-connect a few times though).

    The problem is intermittent and hard for me to know what the issue is. I've tried cleaning the ground cable from the battery terminal over a year ago but that didn't seem to do the trick as it still happens to this day.

    I'd be very grateful if anyone help me to diagnose the issue as it's been happening for so long that I've gotten used to disconnecting and re-connecting. However, since the issue with the electrics cutting out while driving last night, I'll now have to take it more seriously and get to the bottom of this once and for all.

    Would be really grateful for any help as it's stressing me out.

    -----------------------------

    Edit: Battery is only 1 yrs old (and even used to happen when it was new), so highly doubt it's a battery issue.

    Voltage info from the vehicle dash last night:
    • Engine Off: 12.3 V
    • Engine on: 13.7/8 sometimes 13.6 V
    • When driving: 14.2 V

    Vehicle: 2003 C200 Kompressor, Coupe, 1.8L, Petrol, Manual (W203), 133,000 miles
     
  2. LostKiwi

    LostKiwi Senior Member

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    Location:
    Midlands / Charente-Maritime
    Your Mercedes:
    '93 500SL-32, '01 W210 Estate E240, 02 R230 SL500 (Malcolm Spec), 04 Smart Roadster Coupe
    Bad earth, loose battery connection would be my picks. Undo the earth cables where they bolt to the body and clean them and refit with a liberal coating of grease.
    Also look for the earth for the main ECU harness and do that too. There's an earth point behind the headlight thats known to give issues on some cars too.
     
  3. mattkh

    mattkh Senior Member

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    England
    Your Mercedes:
    W168 1999 1.6
    Two things come to mind.
    In the old days, German cars used to have what was called 'cut off relay'. This relay used to cut off the electric to radio, heater, etc, so that all the current from the battery went to the starter motor. I am not sure if your car has this relay.
    Secondly, could it be the ignition switch??
     
  4. thebiglad

    thebiglad Senior Member

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    Location:
    Central France
    Your Mercedes:
    2005 CLK 270 cdi
    My vote would be for the ignition switch.

    However, I note :

    "Voltage info from the vehicle dash last night:
    • Engine Off: 12.3 V"
    This seems a bit low ??
     
  5. thebiglad

    thebiglad Senior Member

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    Your Mercedes:
    2005 CLK 270 cdi
    Just came across this which might be useful:

     
    Last edited: Nov 10, 2018 at 4:45 PM
  6. M80

    M80 Senior Member

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    Your Mercedes:
    Viano 3.0 ExLWB (09)
    I would want to eliminate the battery. Testing voltage at the battery during the attempted start is easy enough with a DVM.

    There is good chance that a couple of relays or more are dropping out due to low voltage, that could be battery or as LK a bad earth that shows up when the higher load tries to pass through it.
     
  7. thebiglad

    thebiglad Senior Member

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    Your Mercedes:
    2005 CLK 270 cdi
    The video link shows what COULD be the problem.
     
  8. brianbrian

    brianbrian Senior Member

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    cockney in the West Country
    Your Mercedes:
    w124 250D, SL129-deisel
    I had your problem, thought it was the alarm playing up. But as.already suggested, turned out to be ignition switch.
     

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