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Retrofit 3rd brake light on W124

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by jeremy156, May 15, 2019.

  1. jeremy156

    jeremy156 Senior Member

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    Location:
    Southampton, UK
    Your Mercedes:
    C209 CLK500 (2004), W124 320E (1993)
    My 1993 W124 320E (pre-facelift) does not have a high level brake light fitted.

    In considering adding one, I'm aware that the cruise control disengages when the brake light illuminates and as such I'm wondering whether it's a safe bet to simply add an LED brake light in parallel with one of the brake light bulbs, or whether that'll confuse things for the cruise control...?

    I'd imagine the N7 bulb-out-warning module probably has a separate output pin for 3rd brake light, which presumably doesn't then relate to the cruise control (big assumption), but I don't know which pin to try and trace a cable path for... and whether it's likely that wire would be in place and simply not used at the rear... or whether I'd need to run a new cable.

    Does anyone have a working understanding of the N7 to help me figure this out, please?

    Cheers,
    Jeremy
     
  2. d215yq

    d215yq Senior Member

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    Barcelona
    Your Mercedes:
    1987 W124 300D 250k
    No idea how the N7 works and but the PO put in a 3rd level brake light in my W124 and wired straight to one of the clusters (forget which one) and the bulb replacement doesn't come on in driving, and did come on when one of the bulbs blew so I'd imagine you's have no problems on that front.

    Again no idea how the cruise control works either but I'm guessing it disengages when the brake switch tells it to and it's nothing to do with the brake lights circuit at all?
     
  3. OP
    jeremy156

    jeremy156 Senior Member

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    Your Mercedes:
    C209 CLK500 (2004), W124 320E (1993)
    Reading around.... the author of (http://www.peachparts.com/shopforum/2591451-post7.html) refers to a dependency on grounding via the brake light bulbs... it sounds like it simply needs at least one bulb to be working to function and that an LED 3rd level brake light in parallel therefore wouldn't hurt.... I will experiment and see...

    Meanwhile, does anyone know where to find schematic diagrams?
     
  4. DREAMER NO2

    DREAMER NO2 Senior Member

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    Your Mercedes:
    W124 2.6E M103 1989
    I would be interested to find out just what type of light the Jeremy will use and the place on rear shelf it will be fitted to .
     
  5. OP
    jeremy156

    jeremy156 Senior Member

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    Your Mercedes:
    C209 CLK500 (2004), W124 320E (1993)
    OK, tried it and it seems that having a (cheap and nasty) LED array wired in parallel with the feed from a light cluster is fine, the LEDs light quickly, the incandescent bulb still illuminates in the expected time and crucially the cruise control still works.

    I'd like to replace the incandescent brake lamp pair with LEDs (for the quicker switch-on), but suspect that would upset the cruise control.... might experiment for amusement...
     
  6. Craiglxviii

    Craiglxviii Senior Member

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    Your Mercedes:
    W215 CL500 Motorway Queen; W251 R320L Familybenz, S211 E320 Avg Designo Edition now sadly missed.
    Would also be illegal.
     
  7. OP
    jeremy156

    jeremy156 Senior Member

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    Your Mercedes:
    C209 CLK500 (2004), W124 320E (1993)
    Thought you might say that Craig ;) Presume you're referring to the pair of brake lights.... do you have a view on retrofitted 3rd brake light?
     
    Last edited: May 16, 2019
  8. Craiglxviii

    Craiglxviii Senior Member

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    Your Mercedes:
    W215 CL500 Motorway Queen; W251 R320L Familybenz, S211 E320 Avg Designo Edition now sadly missed.
    It’s an addition not an alteration, and subsequent model years of your car did have them, so that’s all fine ;)
     
  9. OP
    jeremy156

    jeremy156 Senior Member

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    Your Mercedes:
    C209 CLK500 (2004), W124 320E (1993)
    Right, so that's key... changing something that was put there my Herr Benz is wrong... but no problem adding something new. Crystal clear, thanks mate. How's little'un?
     
  10. Craiglxviii

    Craiglxviii Senior Member

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    Your Mercedes:
    W215 CL500 Motorway Queen; W251 R320L Familybenz, S211 E320 Avg Designo Edition now sadly missed.
    He has a cold and isn’t sleeping, so we’re both like the Walking Dead this week!
     
  11. OP
    jeremy156

    jeremy156 Senior Member

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    Your Mercedes:
    C209 CLK500 (2004), W124 320E (1993)
    Deep joy.... keep your chin up!
     
  12. DREAMER NO2

    DREAMER NO2 Senior Member

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    Your Mercedes:
    W124 2.6E M103 1989
    Yes and so lucky,, so dont let those sleep less nights get you down .I would never know the feeling of such bliss .
     
  13. LostKiwi

    LostKiwi Senior Member

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    '93 500SL-32, '01 W210 Estate E240, 02 R230 SL500 (Malcolm Spec), 04 Smart Roadster Coupe
    The rule is that any light assembly that carries an E-mark must have the appropriate E-marked light source(s).
    If you're adding a third light technically it should also be E-marked but it's a little more open to interpretation.
     

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