R107 SL headlamp wiper electronic motor (coil type) repair

Discussion in 'Electronics' started by SilverSaloon, Mar 18, 2009.

  1. SilverSaloon

    SilverSaloon MB Club Veteran

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    Hi

    I've started to dismantle and try and fix my broken wash/wipe system on my 107.

    I removed the whole unit from the car and went to test it with Red wire to Pos but the motor just appeared dead - no sound or anything. even if it was siezed i'd expect to hear something happening, so I decieded to dismantle the motor.

    The motor seems a simple unit with a coil, magnet etc. Now, i know very little about electronics but there doesnt seem to be much to the unit apart from the resistor(?) - the little black box thing shown in the pic below:

    [​IMG]

    [​IMG]

    The motor coil bit:

    [​IMG]

    Any ideas from our electronic experts out there?

    Any idea on where to get a replacement resistor thing? It has 'G65' marked on it along with '69J 017'. Its about 1cm in size.

    it cant be that hard to fix the motor can it? The main cog thing isnt siezed and if you manually turn the coil when the rack is in position, the main cog slowly turns.

    Thanks!!

    Derek
     
    Last edited: Mar 18, 2009
  2. popuptoaster

    popuptoaster Hardcore MB Enthusiast

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    Maplins may be your best bet i reckon,
     
  3. OP
    OP
    SilverSaloon

    SilverSaloon MB Club Veteran

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    any idea on what i'm looking for? is the black thing marked G65 a resistor, capacitor - what is it called? sorry i know very little about electronics!
     
  4. popuptoaster

    popuptoaster Hardcore MB Enthusiast

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    Me neither, take it with you, they should know what you need to replace it even if its not exactly the same.
     
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  5. Dieselman

    Dieselman Banned

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    It's probably just a fuse. Check continiuity, if open circuit bridge it to test.

    If it has one leg connected to Gnd then it's a supressor (capacitor) to stop radio interference.
     
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  6. OP
    OP
    SilverSaloon

    SilverSaloon MB Club Veteran

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    i checked with a multimeter and after the thing there is no current.

    am i right in thinking this is a very simple mechanism?

    could I just hook up 12v to the two metal springy things that go around the "rack" and then see if it spins the magnetic coil thing? sorry for my lack of knowlege!!!
     
  7. Ted

    Ted MB Club Veteran

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    This is guesswork only.........
    I think that the resistor is a thermal cutout, designed to protect the motor if the linkage has jammed (frozen, accident etc)
    Therefore if it is o/c it has failed.
    That means that it will be ok to put 12v across the motor terminals. Keep clear of all parts, because as the motor is geared down, I would expect it to be very powerful. (not fast, just a lot of power at the linkage.

    Oh, and just to get ever so slightly techy........
    It looks like a permanent magnet motor.
    The 'rack' is the commutator (sp?)
    the springy things are the brushes (I bet you knew that really) :0)
    the twirly thing is the armature.

    If the armature was burnt out, you would know it - it would be black, and smell very burnt. You CAN get it tested at a good auto electrician. Ask them to test it on the 'growler'.
     
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  8. OP
    OP
    SilverSaloon

    SilverSaloon MB Club Veteran

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    Thanks for everyone's help & advice on this. Last night I got it working. It basically just needed a good clean up.

    I cleaned the grooves out and cleaned the surface from this:

    [​IMG]

    to this:

    [​IMG]

    I also cleaned the brushes with some sandpaper.

    And now it just works! I intend to grease all the cogs etc.

    I then dismantled the other parts of the unit to reveal a lot of siezed parts - basically the motor pushes a rod along the pipes that turn the cogs and turn the wipers.

    Some pics of how it was inside the mechanisms:

    [​IMG]

    [​IMG]

    [​IMG]

    and after a degrease, some of the parts ready to be re-assembed (with new grease):

    [​IMG]
     
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  9. Ted

    Ted MB Club Veteran

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    Result!!
    I love it when you can actually fix something.
    Well done.
     
  10. OP
    OP
    SilverSaloon

    SilverSaloon MB Club Veteran

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    yeah quite satisfying as i really wanted to keep the spec of the car as it was when it was new. it will be great to see the headlamp wash/wipe system working on the car. by the look of things it appears it hasnt worked for some time. previous owner said it has never worked when he had it.

    One of the cables that go through the pipes looks like its been worn away/forced at some point and some grooves cut off. £10 for a new one so i will just replace to be on the safe side - it may be fine but its a lot of hassle to remove it all again at a later date. Also need about £15 worth of other bits and bobs (wiper rubber, some minor bolts etc).
     
  11. popuptoaster

    popuptoaster Hardcore MB Enthusiast

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    Well done, i do love a good repair rather than replacement. :D
     
  12. OP
    OP
    SilverSaloon

    SilverSaloon MB Club Veteran

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    hehe replacement wouldnt have been an option as its £600 new from MB, and getting working 2nd hand ones would be hard i suspect. this was my main concern as i really didnt want to remove the unit from the car.
     
  13. Pie-Man

    Pie-Man New Member

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    Hi there!

    Just starting to try and repair the headlamp wash/wipe on the girlfriends 89 300SL ... dumb question, but ... how do you remove the wiper mechanism from the motor? I've detached the motor from the car mechanically and electrically, but haven't sussed out how to get the motor & total mechanism off the car?

    Cheers!

    Tim
     

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