DOH! I must've messed up interior light wiring

Discussion in 'Interior' started by S9KSY, Jul 23, 2010.

  1. S9KSY

    S9KSY Hardcore MB Enthusiast

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    E280 Estate Automatic W124 1995
    I replaced one of the tailgate gas struts and tailgate function is now superb.
    However, the lights of the trunk, the d- and the c-pillars stay on.
    I tried all combinations of control switches (see below) with no response.
    I must have screwed somthing up. :doh:
    There were no problems with these lights prior to my DIY. :eek::eek::eek:
    The rear demister didn't work and still doesn't. Demister is not my top priority at the moment.
    I disconnected the battery for now.
    I hope I find a solution, otherwise, I will have to remove these bulbs.
    Any suggestions? :confused::confused::confused:
    [​IMG]

    I tried all combinations of lights controls. They stay on!
    [​IMG]

    The button on the right, nearest to ignition key has no effect. :dk:
    [​IMG]
     
    Last edited: Jul 23, 2010
  2. Druk

    Druk Administrator Staff Member

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    The auto switch for these is integral with the tailgate self-closer motor. Have you messed with that or with the wiring junction strip under the rear removable part of the headling?
     
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  3. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    I have not touched the locking mechanism.
    I did detach the complex connection under the headlining (unnecessarily, because I did not change the whole tailgate door as I originally intended). All wires are colour coded and numbered. You can't go wrong supposedly. I double checked and all wiring seem to be where the should.
    [​IMG]
     
  4. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    The picture above is for BEFORE I detached any wires.
    There is a thickness of black plastic right under the left 5 screws. What you see there is NOT a shadow.
    I am not absolutely certain but I think something fell off from underneath the contraption when I removed it.
    I think I did not insert it back.
    It did not look much. It did not seem to be serving any function.
    Having thought of it now, I think it could be an insulator.
    I will take a photo of that weird curved oblong plastic piece that has many small holes tomorrow. I still have it laying somewhere.
    Probably someone on the forum knows what it is for.
     
    Last edited: Jul 24, 2010
  5. cyberflex

    cyberflex Hardcore MB Enthusiast

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    Could it be that there is a contact problem? When you have time, remove one by one, each 'eyelet'/'spade' connector and clean each ones surface carefully with some form of contact cleaner, then re-seat them so they are 'happy' and making good contact, try not to overtighten the terminals, but nip them up enough so that they will stay 'contacted', if you know what I mean, also may be worth triple checking the wiring sequences after a good nights rest, it is easy enough to mis-connect, if one is tired. Finally check if there is any loose contact on the 'crimped' ends, sometimes the copper deteriorates internally and the sheath is the only crimped material.

    The elusive plastic piece could also be a factor.

    All seems pretty obvious and I know you are more than capable from your previous posts, but sometimes tiredness can be to blame.:thumb:
     
    Last edited: Jul 24, 2010
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  6. Druk

    Druk Administrator Staff Member

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    Maybe that is the problem. I don't have my 124 anymore and am just digging into old memory.
    BTW, I wasn't suggesting you had 'messed' up, just pointing you at a possible reason for the problem. Sorry if I gave the wrong impression.
    Your 'contraption' suggestion is possibly correct in that it's probable the wiring from the lights is 'earthed' by the tailgate locking mechanism and it's likely the wire is grounded before it gets to the switch.
     
    Last edited: Jul 24, 2010
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  7. corned

    corned Hardcore MB Enthusiast

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    I think this is a good spot to start. If that piece is indeed an insulator, then the ends of the 5 left-most screws could be in contact with the body, thereby grounding the circuits and effectively bypassing the switches!

    If you can detach that terminal block and hold it away from the metalwork of the body, does the problem go away?
     
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  8. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    With a skin thicker than a rhino’s and brains functioning slower on occasions. I did not even notice.

    You will also notice that I was the first to come up with the “mess up” phrase in thread heading. Later, a “screwed up” phrase was also mentioned by me. Apologies for my French
    Fantastic suggestions.
    Thank you Druk, cyberflex and corned
    I am now off to remove headlining, do as advised and will publish a picture of that strange “insulating” contraption this afternoon.
     
    Last edited: Jul 24, 2010
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  9. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    Update....it was a red herring!

    In the posts above, I was roving about this strange looking black plastic that I decided it must have fallen off the electric connection, and how I regret not putting it back in place?
    Remember?
    Well, I was wrong! :eek: :eek: :eek:
    Here is what I was talking about.
    [​IMG]

    Here is the rest of it. As you can see, it is clearly a broken piece from the clipping belt of W202 headlight.
    [​IMG]

    If you look at its shape (the piece on the right) you will see why I mistakenly assumed it could be related to the tailgate electric connections
     
    Last edited: Jul 24, 2010
  10. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    Electric connections are absolutely fine. THE PROBLEM IS STILL THERE. LIGHTS STAY ON.

    This is how it looks today.
    I revised each connection and everything was where it should and there doesn't seem to be any bad connection.
    [​IMG]
     
    Last edited: Jul 24, 2010
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  11. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    where is the switch that will tell the car that tailgate was open or shut?

    I think the problem is with the system that recognises that the tailgate was shut or open..
    I believe the car still thinks that the tailgate is staying open, hence keeps the rear interior lights stay on, and alarm sounds off whenever I want to lock with the remote.
    The C and D pillar lights electric source comes directly to them and is completely unrelated to the complex tailgate electric connection above.
    [​IMG]
     
  12. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    I looked inside the tailgate, and the central locking yellow vacuum tubing is connected and functioning well.
    I found this relay in the tailgate on the left and was wondering whether it was the reason.
    I replaced it with the relay I cannibalised from my spare W124 but the problem was not solved.
    I have no idea whether the cannibalised relay was working.
    What does the tailgate relay do there?
    How do I know whether it is working or not, short of buying a new one?
    [​IMG]
    [​IMG]
     
    Last edited: Jul 24, 2010
  13. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    I just checked part number "124 821 00 63"
    It is the rear wiper relay.
    There is no problem with the rear wiper function.

    I still do not know how the car knows that the tailgate was open or shut.
    I am sure the problem with that switch or sensor.
    I looked carefully. No buttons or switches I could see.
    I hope someone could help.
    Please?
     
  14. Druk

    Druk Administrator Staff Member

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    I think the tailgate relay has something to do with the rear wash/wipe. There is a microswitch as part of the tailgate close assist and puts the interior lights off/on. Certainly did on my 93..
     
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  15. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    Thanks Druk. The tailgate is fully open and can see all the locking mechanism in front of me. However, there isn't anything resembling a switch.
    I feel that the problem is with this sensor / switch.
    The reason I can't find it is probably because I have no idea what I'm looking for.
    How can I fix this microswitch. Err...ahem...I suppose I have to find it first....Where is it? Any idea?
     
    Last edited: Jul 24, 2010
  16. Druk

    Druk Administrator Staff Member

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    I think you'll have to take the lock mechanism out of the tailgate to get at it. It's quite a feat of engineering once you see it. There is a small motor and a couple of limit switches and all sorts of gubbins. You can make it operate in place by pushing the latch over the first position with a screwdriver. Possibly the reason your alarm is arming is because it has a sensor on the interior light switches or is voltage sensing. I don't think the car is clever enough to have to 'know' when the tailgate is shut or not.
     
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  17. Druk

    Druk Administrator Staff Member

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    Further to this..a wiring diagram I have for an early W124 230TE shows the wire Brown/Grey comes to the motor via the roof connector block straight from Left Rear Door Switch which is in parallel with RRDS and is fed from T7 on the dome light switch on the dash. It's obvious from the drawing that microswitch s2 on the lock acts as an ground to the lights as do all the door switches. Disconnecting the brown/grey at the roof terminal block will isolate the fault to either the lock or one of the door switches (or the dome switch.)
    Microswitch s2 is not a powered switch but is actuated by some part of the lock moving to the locked position.

    edit. the other possibility is that the brown/grey is trapped/fractured somewhere along the tailgate wiring loom (at the hinge is not uncommon) and that it is making to ground which would have the same effect. Once again, dissing it at the block would prove.


    .
     
    Last edited: Jul 24, 2010
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  18. OP
    OP
    S9KSY

    S9KSY Hardcore MB Enthusiast

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    Thank you Druk
    I must admit that there are some parts of your post that I am unsure of.
    Probably all will be clear if I see the diagram
    Please correct me if I am wrong. From what I understand, you are suggesting disconnecting the first cable on the left (brown/grey).
    Your post appeared to suddenly terminate. Is there something missing or am I misunderstanding?
    The roof terminal block is numbered and I am wondering whether the T7 and S2 mentioned in your post are meant to be the cables in 2nd and 7th position.
    The other parts from your post I am not sure of:
    RRDS
    dissing: I googled it and it came as “slang for disrespecting”, which happens to give the same connotation here if it were a typo for “disusing”

    Anyway, I will disconnect the brown/grey cable tomorrow morning and see what happens. You seem to know what you are talking about and I am grateful for your help.

    Thanks again
     
    Last edited: Jul 24, 2010
  19. Druk

    Druk Administrator Staff Member

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    Dissing is disconnecting in sparky speak.
    T7 is terminal seven on the dome switch.
    s2 is the number on the microswitch mounted on the tailgate closure motor
    RRDS...right rear door switch. opposite Left Rear Door Switch in post. Just trying to save myself some typing.....
     
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  20. Pontoneer

    Pontoneer MB Club Veteran

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    The tailgate electrical closing mechanism ( behind the lock ) has at least two microswitches in it and you should hear it motoring open and closed when you open and close the tailgate . They do suffer from water ingress and I have had to replace two of these on different estate cars . You would need to remove the lock assembly from the bottom of the tailgate to see what is going on . The microswitches are on the outside of the mechanism but inside the tailgate . It is a bit of a fiddle to remove the assembly due to mechanical linkages , but the problem is likely to be there .
     

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