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W203 Auto lights.

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by Paul Goff, Feb 11, 2018.

  1. Paul Goff

    Paul Goff Senior Member

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    2002 C220CDi CD Estate
    Hello again everyone,

    My 2002 W203 C220 CDi has auto lights and I usually just leave the switch in Auto and the system to it's own devices, but I do keep an eye on what it is doing (or not doing).

    However, there are times when it appears reluctant to turn the lights on and also somewhat keen to switch them off again! This seems to be a little counter intuitive, I would expect them to be keen to switch on and reluctant to turn off! My limited experience of other cars is that they behave in the latter manner.

    My question is this, what, in a nutshell are the operating parameters of my system?

    Light level.
    Light level and auto wipers activity
    Light level, wiper activity and speed
    Anything else?
    Any permutation of the above?

    Yesterday I sallied forth in a heavy rain storm, at about mid day, but the lights did not switch on for a mile or two, while most oncoming traffic was well illuminated! (on a long bypassed and now very quiet former A road)

    Is there a possibility that the parameters can be reset by me, rather in the way that steering angle, heating flaps etc can be? Or by a genius with a STAR machine?

    I must stress that it always activates the lights immediately after starting if it is properly dark, also the Find Me & Light Me to the door functions via the fog lights both work well.
     
  2. OP
    Paul Goff

    Paul Goff Senior Member

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    tap tap tap tap......tap.....tap???

    I knew it was a pretty obscure question!

    Anyone??

    Pretty please lots, kissy kissy.
     
  3. mercedes13156

    mercedes13156 Senior Member

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    Your Mercedes:
    CLK 200 Cabrio and a Ford Kuga
    Sounds like the light sensor to me. If you're not getting an error message in the dash, then to all intents and purposes, it is working fine. It tends to lurk in the back bit of the windscreen, between the glass and the plastic cover behind the rear view mirror and you'll recognise the 8 little silvery circles. It might not be getting enough light, so clean the glass thoroughly. That bit doesn't get wiped, so there might be a buildup of crud on the glass.

    If cleaning doesn't work, the next cheapest option is to look at the relay which is activated by the sensor and turns the lights on and off. It might be getting a bit tired and not too keen to work as it should. Failing that, the answer is the sensor itself.
     
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  4. OP
    Paul Goff

    Paul Goff Senior Member

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    Thanks for the input 13156 (sounds like a Fiat/Alfa cross to me :))
    I can't see eight silvery circles though, at the top centre of the screen are one little blue ish rectangle, one small silver round and a small and large silver pair. I assume the silver pair are for the auto wipers, working on refraction/reflection of rain drops?

    My car has auto lights, wipers and electrochromic mirrors, I think I will have a little tinker with the sensors and some tape, just to see which is which!
     
  5. davemercedes

    davemercedes Senior Member

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    Your Mercedes:
    2007 Merc 220 CDi Est Auto Av
    Hi Paul

    I have an S203 and tend to leave my lights on Auto as well but I must admit it's not quite as keen on turning them on as I might like. On Tuesday, the weather was persisting down and I noticed that most people had lights but on my car the lights obstinately stayed off. I turned them on manually which is unusual, but it was a yukky day and most of the time they do enough to keep me happy. There's no way AFAIK to vary the sensitivity or timing of the sensor controls via the on-board computer settings (we can literally enable or disable them) but something may be possible within STAR?

    - Maybe someone familiar with STAR can answer that?
     
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  6. Paul1948

    Paul1948 Senior Member

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    S320 CDI 2003
    Has the windscreen been replaced at any time, if it was has it been reset on Star as this isrequired to calibrate the new screen.
     
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  7. Ken_R

    Ken_R Senior Member

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    Mine's quite the opposite. They come on before I'd normally switch them on. Is it possible that they are Factory calibrated according to the colour 'tone' of the vehicle. Dark coloured vehicles can be less easy to pick out as the light fades and Greens will tend to merge more in rural road settings.

    One thing that I recently noticed with Automatic, is that they don't come on in daylight thick Fog. The sort of Fog where you can't see very far in front, but the ambient light level is still high.
     
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  8. rf065

    rf065 Senior Member

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    That's because light is reflected of fog and the sensor thinks it is still daylight.

    Russ
     
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  9. davemercedes

    davemercedes Senior Member

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    Hmm... I'll watch out for that over the next few days. Down in Glos on Thursday it was quite foggy in places - as usual, especially down the lanes where the odd idiot comes flying up in the opposite direction like there's no tomorrow (and one of these days there won't be!).
     
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  10. EmilysDad

    EmilysDad Senior Member

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    My auto lights are often on at dawn with a low sun
     
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  11. OP
    Paul Goff

    Paul Goff Senior Member

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    I have been playing about with the sensors and some packing tape.

    The Auto Dim Mirrors work from sensors front and back of the interior mirror itself, this works well.
    The Auto Lights work from the little & large pair of silver sensors, covering both with tape switches the headlights on within a few seconds, removing the tape switches them off. Covering just one doesn't seem to do anything.
    The Auto Wipers work from the little silver sensor (transmitter?) and the large blue one (receiver?)

    Obviously this is a very crude way to test things but it does prove that everything is basically OK.

    I have no idea whether the screen had been replaced prior to my ownership but if the sensors need a STAR reset after a change it does tend to point to the possibility that these things are possible to recalibrate.
     
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  12. davemercedes

    davemercedes Senior Member

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    Does SWMBO know about you visiting Dawn?
     
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  13. OP
    Paul Goff

    Paul Goff Senior Member

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    Is it possible that they are Factory calibrated according to the colour 'tone' of the vehicle. Dark coloured vehicles can be less easy to pick out as the light fades and Greens will tend to merge more in rural road settings.

    Mine is Obstinate Black :)
     
  14. EmilysDad

    EmilysDad Senior Member

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    I wish ..... ;)
     

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