W124 Dashboard and switch illumination

Discussion in 'Electronics' started by GP801, Jan 29, 2016.

  1. GP801

    GP801 MB Enthusiast

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    The 124 went for its service and MOT today. Passed with no advisories! However one of the little jobs done was to replace the passenger side air vent light bulb. Old bulb well and truly black. New bulb fitted, lights up but flickers. Attempts to adjust contacts so it contacts better but now nothing illuminates on the dash - air vents, heater controls, window switches. Warning lights on cluster working fine. Ashtray light and dome lights fine. Switches and controls all still work correctly - just not illuminated. Fuses all good - they were all replaced just in case.
    Any ideas folks? Dimmer control/resistor? Any other thoughts
     
  2. Ted

    Ted MB Enthusiast

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    Have you tried turning the dimmer up and down a few times?
     
  3. llewe

    llewe Active Member

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    Mine did just this and there was a degraded solder joint on the printed circuit
    board in the dash that was the culprit. Another possibility is the rheostat is knackered.
     
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  4. whirsk

    whirsk Active Member

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  5. OP
    OP
    GP801

    GP801 MB Enthusiast

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    Thanks for the replies. Turning the dimmer makes no difference. I think the plan will be to replace the dimmer control as the first step.
     
  6. Ted

    Ted MB Enthusiast

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    As the illumination on a w124 instrument panel is so low, you could just bypass the rheostat.
     
  7. MB-tex

    MB-tex Active Member

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    Hi

    This happened to me when I changed a fuse behind one of the heater knobs. All the console lights stopped working. Lights on clocks still worked as far as I remember. The cure is a small red plastic fuse behind the clocks that needs changing. Do a google image search for "console lights w124 red fuse" and you will see where it is.

    The clocks need to be pulled (coat hangers cut and bent to shape) and the speedo cable needs undoing to give you access to get the little fuse out and in. Some w124 cars I believe have the speedo cable running up under the carpet by pedals that can be loosened to give slack on clocks as they come out of their housing. On my 96 W124 I could find no speedo cable accessible. This is only becomes a problem when re-attaching mechanical speedo cable when putting clock back in (or leave it off to increase resale value!) as on mine there was very little slack to pull into place to tighten the ring onto the threaded speedo back and space is very restricted behind clocks and steering wheel. It was a REAL PAIN and required huge patience and thought. Very satisfying when it finally worked though but left me with a aching back and sore hands...Other electrical plugs easily detached and re-attached onto back of clocks. An easy job really and those console lights look lovely.
    Google w124 speedo removal and all you need to know will be revealed.

    Good luck
     
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  8. OP
    OP
    GP801

    GP801 MB Enthusiast

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    Thats very useful thanks. I have left it in the capable hands of the Indie to sort out but have passed the info on just in case he has not come across it before.
     
  9. OP
    OP
    GP801

    GP801 MB Enthusiast

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    Well it turned out this was a really odd one. There was no fuse on the back of the console. The dimmer/rheostat was fine. A cable on some module deep in the bowels of the centre console had disintegrated. To avoid having to completely dismantle the interior it has been rigged with a new feed activated from the radio. So to have the console lights on I need the radio on. Not a problem as its always on for the bluetooth phone connection. So all set to return to Italy next week.
     
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