Bonnet open warning

Discussion in 'Bodywork' started by thebook, Jan 22, 2018.

  1. thebook

    thebook Hardcore MB Enthusiast

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    Morning all,

    I topped up my screen wash at the weekend and when I started the car this morning, the bonnet open warning light was on (centre screen red with an image of an open bonnet).

    I got out and checked but it was definitely closed. I released the bonnet and slammed it shut but this made no difference. I then drove to work with constant alert bongs (which was painful). Any tips on how I rectify? I plan to spray all hinges/locks with WD40...
     
  2. Dec

    Dec Hardcore MB Enthusiast

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    What year is the car?

    Try locking the car with the remote and see if the hazards flash 2 times or 3 times.


    Dec
     
  3. Riva811

    Riva811 Hardcore MB Enthusiast

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    Same thing happened to me because I tried to be gentle. I opened the hood again and let it fall from 30cm and it worked.

    Sent from my G8141 using Tapatalk
     
  4. OP
    OP
    thebook

    thebook Hardcore MB Enthusiast

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    E350 CDI Cabriolet just replaced my 997 C4S
    Thanks for the replies. The car is a 2011 A207 (E Class Cab). I will check how many times the lights flash when locking. The internal catches seem very
     
  5. ioweddie

    ioweddie Hardcore MB Enthusiast

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    Just re open it and drop it closed with a little push
     
  6. grober

    grober MB Club Veteran

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    Check the bonnet catches- at least one of them has a switch incorporated in it.
    [​IMG]

    similar to this
    [​IMG]
     
    PaulXC and John N like this.
  7. OP
    OP
    thebook

    thebook Hardcore MB Enthusiast

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    E350 CDI Cabriolet just replaced my 997 C4S
    Thanks everyone for your swift replies. I can confirm a liberal squirt of WD40 on the areas highlighted in the above diagram seems to have done the trick! All good in my world now, no more annoying bongs...
     
  8. 190

    190 Hardcore MB Enthusiast

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    That's odd as I had the same problem recently. When I removed the contact sensor shown in the photo above there was a tiny bellows seal on the micro switch operating pin which looked like it would prevent WD40 from getting inside the switch. What I did instead to ensure the switch was being actuated properly was to bend the leaf spring slightly (visible just to the right of the epoxy resin) that transfers the movement of the bonnet catch to the micro switch pin and that cured the problem. I also greased the mechanism while I was in there.
     
  9. OP
    OP
    thebook

    thebook Hardcore MB Enthusiast

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    E350 CDI Cabriolet just replaced my 997 C4S
    There catches were so tight there was no spring in them. I guess the WD just provided sufficent lube to loosen them up. They now spring and all is good.
     
  10. grober

    grober MB Club Veteran

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    If the problem comes back you could try a light persistance type spray grease such as a lithium /teflon containing one as WD may get washed away. Halfords stock a range of these or your MB dealer can advise.
     
    thebook likes this.
  11. topdown

    topdown Hardcore MB Enthusiast

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    Make sure the release handle is pushed back after opening.
     
  12. brianpaul

    brianpaul New Member

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    Sep 18, 2011
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    slk230
    This problem is an easy fix on my w212 e class all you need to do is lengthen the bonnet catch on each side by adjusting the 13mm nut so the catch gets slightly longer and this will push the sensor down more when the bonnet shuts.
     

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