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Electrical Diagram for Horn Circuit

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  • Electrical Diagram for Horn Circuit

    If you like puzzle, and if you know the electrical diagram of early smarts, please use your intuition to try solving this problem.
    What I mean by early smarts is the ones with ZEE module (2002). For SAM controlled smarts is a very different problem
    History of the problem
    I bought a smart car with the ZEE burned, not sure what caused that at the time. I thought that an accidental jump start, accidental water spillage, etc
    I replaced the ECU/ZEE/ etc, the car started fine, worked fine, expect for the clock (the one that keeps time on top of the dash) and the locking/unlocking of the doors (including the rear glass boot door)
    Strangely enough, they are all fed by Fuse 16, a 15AMP fuse. The fuse was fine, no damage etc. On the same fuse it was the Horn, and also the interior lights (Horn and interior lights worked fine anyway)

    I changed the door actuators(all 3 of them) and the clock and it seem that problem solved. The car worked fine for another few months, locking unlocking, horn worked fine, etc

    All of the sudden, while driving in the rain the car started to sound the horn continuously, my wife was driving at the time. for an hour the horn sounded, she stopped the engine, she took the key out, the car was horning (7am on a residential road). AA came, disconnected the battery and recovered the car home
    arrived home in the evening: short diagnostic, connect the battery horn on . disconnect the battery horn off. Then unplugged fuse 16, connected battery, the car drives fine , no problems, except for locking and unlocking and obvious the horn

    Took steering wheel off and the black ribbon wires completely burned and melted (only the horn ones, the other 2, air-bag were still fine). At that time, I did not properly understand the Horn circuit (not that now I understand it). I thought, unlucky, the steering wheel button accidentally pressed by wife, horn engaged, high current passing for a while, heath produced, wires melted, horn remained engaged. Now I know how wrong my diagnostic was.
    I now know that horn wires on the steering wheel go to relay D, and that the horn is on ignition
    So, why on earth the horn sounded with ignition off?
    so, repair, changed the squib, put the fuse back on, and car working fine; lock/ unlock/ horn operating fine
    until another rainy day(wife driving) wipers stooped working, air-bag light on
    wipers fuse was burned(replaced right away and wipers fine after)
    squib completely burned, horn not working
    it could be a coincidence, but I believe it is something more than just coincidence, I believe that somewhere is a wiring fault that makes the squib hot and melts the wires inside, but I am not electrician, I am a regular DIYer (form a technical background - computer science) that likes solving puzzles,
    I need more pieces if I will ever be able to solve this puzzle
    I have the evolution horn wiring diagram, but that only covers the horn and only for SAM cars (completely different )
    Now the car is without a squib on the back of the steering wheel and works fine expert horn and drivers airbag
    not sure if the fault is on the horn circuit
    it might be on one of the doors, etc
    it is now clearer to me that the previous ZEE might have been burned by the same fault; it is also unlikely that all 3 doors actuators to be dead on natural
    so far I know
    ZEE fuse 16 feeds into interior lights, door actuators, horn relay, clock -- all of them burned either while the car was mine or right before that
    fuse 16 never burned
    2ice the steering wheel squib was melted and and short circuited ( while driving in the rain- might be coincidence)
    I am tempted to:
    remove the Relay D(horn), rewire the horn, squib right to another relay, relay right into the horn(new horn, new relay, new wires)
    but the horn circuit might not even be the problem
    To try figure what is going on I made this simple hand drawn note, it might be completely wrong, I assumed that steering wheel buttons switches the earth and the relay is switching the 12V

    PS: I do not expect find the exact problem , it will he hard to find where the wires are damaged; All I want is to understand where the wires can be damaged so that they will be able to burn the actuators, melt the squib, etc; but fuse is intact. It defies logic for me, something like the double slit experiment
    any information might help solving the puzzle, and if I will ever solve this I will post right away the answer

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