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W203 electrical issue.

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by dmolyneux, Dec 16, 2012.

  1. dmolyneux

    dmolyneux New Member

    Likes Received:
    Dec 16, 2012
    Your Mercedes:

    I have a C220 2006 W203 diesel with an intermittent electrical issue.

    Some history, 12 months ago the car had various issues with headlights, instrument cluster and other electricals switching off whilst car underway and battery warning light coming on. Battery checked by roadside assistance and Mercedes dealer, no issues found. Car continued to do this and after several visits to dealer without them finding a fault I asked them to change the voltage regulator on the alternator.

    This seemed to do the trick, car has behaved fine since up until last week or so.

    Battery warning light came on couple of times, radio would switch off and back on randomly and seemed to also trip out when the front wipers activated. When moving ignition key to consumers on the Audio 20 radio would display Low Voltage on the radio itself.

    I figured the original battery was still on the car so I had the dealer replace it but have still had a couple of times the radio has turned off and back on and it has still shown low voltage a couple of times prior to starting the car. The battery warning light however has not come on since the battery was replaced.

    I did some googling and identified that the radio and wipers are controlled from the front SAM. I took a look at this and around the unit seemed quite damp as I think some of the rubber seals by the side of the bonnet had moved. So I have dried off this area but inside the SAM housing itself looks perfectly dry. However as the issues 12 months ago were in the same time of year ( wet,damp cold ) then seems like maybe water ingress or something somewhere.

    I have a third party Viseoo MB-2 bluetooth connected on the car and wondered if that might be related to the low voltage on the radio and plan to try the car with this removed.

    However on further inspection of the SAM the wire that comes into the SAM and connects to connector M15 as per the attached drawing, looks like it has lots of electrical / insulation tape that somehow doesnt look like factory fit. Although I am unaware of any work being undertaken on this. I have had the car three years with full history and purchased from MB main dealer.

    I wonder if anyone has any idea what the issue could be please?

    I wondered if it could be a poor ground for the front SAM but dont know where the ground is located for this? If anyone has any idea I will check it.

    The M15 connector might provide clues if anyone knows what this connector is for?

    The fact that this occassionally triggers each time windows wipe made me wonder if the relays for wipers might be iffy or something or the SAM unit itself?

    Are the relays replaceable without changing the whole SAM unit?

    I wonder if the original suspected voltage regulator issue may have damaged the SAM? Is this possible?

    I would be grateful for any suggestions based on the above, apologies for the long post but figured the more info the better.

    I love the car and just want to sort out this issue.


    Attached Files:

  2. mersum1es

    mersum1es Senior Member

    Likes Received:
    Sep 25, 2010
    Your Mercedes:
    W212/-09/350CDI, W219/-07/320CDI, EX:W220/-01/320CDI, EX:W211/-04/320CDI, EX:W210/-01/270CDI
  3. television

    television Always remembered RIP

    Likes Received:
    Mar 14, 2005
    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    Front SAMs on an early 203 are very troublesome, they can get moisture in them, and this can have the effect of wiping the memory and corrupting other circuits with false readings.

    Insulation tape was never used from new

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