How to.....Horn diagnostics and repair

Discussion in 'How To' started by b0dyr0ck2006, Aug 27, 2011.

  1. Adjusting the Horn
    If the horn has a threaded screw on the back, it's adjustable. You just turn it a little either way until it sounds loudest. This moves the diaphragm closer or further away from the electromagnet inside to get the best combination of amplitude and good vibration of the electrical contacts inside.



    Horn Wiring

    It's amazing what the Haynes and Bentley manuals DON'T tell you. They say absolutely nothing (that I can find) about how the horn wiring works.
    The horn wiring is complicated because the horn button has to be attached to the steering wheel, which must be able to rotate freely. And one would assume that the horn is switched by way of the positive (+) side, which it is not. A copper pick-up (slip) ring is mounted to the base of the steering wheel (hub), and a copper contact is mounted on the turn signal switch. This copper contact on the indicator switch applied pressure against the rotating slip ring, allowing current to pass through. From the copper contact on the indicator switch a brown grounding wire is connected to the horn.
    The horn button connects the floating horn negative side to ground by way of the wire that goes down the steering shaft to the steering box coupler. When the horn button is pressed, the circuit is completed to ground (through the steering box) and the horn sounds. The horn positive (+) side is direct wired to the battery by way of a fuse.
    The horn itself has a 'hot wire' to one contact (has 12+ to it), and the other wire goes through the horn contacts for the grounding. That is, the horn ring/button grounds the circuit, rather than being the more usual active lead switch. I guess it's easier to do the 'ground switch' arrangement through the steering column, as any rubbed leads here will simply activate the horn, rather than shorting an active lead. A blip...blip on the horn as you turn the wheel would forecast a problem-- like a self-diagnosis.


    Horn Operation


    If your horn doesn't sound:
    Screwed on the bottom of the old steering wheel assembly is a brass contact ring with a wire attached that runs to the horn.
    The brass contact on the indicator switch is probably dirty/greasy, and most likely it's not making contact the brass ring you installed on the steering wheel hub. What you need to do is bend the brass tab carefully so it contacts the gold ring. I put TWO bends in it, one to bring it up, and one to "level it off". Make sure it doesn't rub TOO hard, or it will wear through quickly! If it is dirty or greasy, it can be cleaned with solvent on a rag (gently!) and, if necessary, very fine emery cloth.

    Sometimes (especially when turning corners) the horn sounds all by itself:

    Obviously there is some short between the copper disc on the steering wheel hub and the steering column housing, which would act as a ground (the horn is powered all the time and works when grounded).
    The fix for this problem is very simple, and does not require removal of the steering wheel hub. Look into the gap between the hub and the steering column housing with a torch and you will find that the copper disc on the hub is deformed. When the steering wheel is turned just right the copper disc will make contact with the steering column housing (ground) and the horn will sound. (A key inserted into the gap would connect the copper disc to ground and have the same effect.)
    To fix this annoying problem insert a medium flat-bladed screwdriver into the gap and press the copper disc so that it is flat all the way around rather than deformed. Also press it up more firmly onto the splined fitting in the centre of the hub that fits over the steering rod.
     
  2. I've just looked at my Horn underneath the floor plan and have four connections going to it 2 white wires and two black, but ony two terminals?
     
  3. What is the question? The horn has two connections, earth and live. The live traces back to a live and the earth traces back to the horn button.
     

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