Trouble with horn

Discussion in '365 GT4 2+2/400/412' started by thomco80, Apr 28, 2021.

  1. thomco80

    thomco80 Rookie

    Apr 7, 2021
    Full Name:
    Tomas Szemes
    Hi Ferarristi,
    I just got a 1982 Ferrari 400i A and my horn is not functioning. Trying to do some troubleshooting, and I am stuck at the no. 1 step (besides checking fuses) - locating horn compressor.
    According to manual, oil drops should be applied into the blower unit as maintenance. I am fully lost to where the location is. I did not find it behind the bumper grill.
    Thanks for any suggestion.
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  3. raemin

    raemin Formula Junior

    Jan 16, 2007
    Lyon (FR)
    Full Name:
    R. Emin
    Compressor is bolted on the front of the left fender.

    There is a relay for the horn. If the steering wheel button works, you should hear the relay "click" when you press the button. If you do not hear the relay, then you problem is on the steering wheel.
  4. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
    Romulus, NY (Finger Lakes)
    Full Name:
    Ken Battle
    If I assume you are in the US, The air horn may have been disconnected and a "conventional" horn installed in its place. I believe in those years air horns were not legal. My air horn was still fully installed, only the wire re-routed to a Hella horn. My compressor and horn were both behind the grill.

    When checking wiring, remember the wire in the steering column to the button is a GROUND wire. It is real easy to test just by grounding wire to anything. Wire in column is light purple and you can find a connector where column goes just under the dash. (I spent a lot of time getting my horn NOT to honk.)
  5. thomco80

    thomco80 Rookie

    Apr 7, 2021
    Full Name:
    Tomas Szemes
    Many thanks for suggestions, I plan to do the check today.
  6. fez1238

    fez1238 Karting
    Silver Subscribed

    Sep 5, 2007
    Assuming the above may have failed. Check and clean the ground connection inside the horn button inside the steering wheel. It was my problem and solution.
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  8. Part Time

    Part Time Formula Junior
    Silver Subscribed

    Dec 16, 2013
    Port St. Lucie, Fl
    Full Name:
    Gary Shore
    If you still have a pair of air "trumpets" behind the left grill area, follow the pressure hoses back to the air compressor, a small cylinder about the size of a soup can. There should be a hose going to the horns, and a second hose going up to the top of the inner fender as the "intake" hose. Disconnect the electrical connector, hoses and remove the pump. The rotor inside the pump end might look like this if the unit has not functioned in awhile. Clean the housing and rotor and vanes, keeping them in the same position and alignment if possible. Add a minimum of oil over everything and reassemble.
    Test with a couple of wires off the battery and hope its spins, re-install with new hoses and make sure the intake hose will not be drawing rain or moisture from anywhere.
    That should fix the mechanical portion, the rest is all electrical.


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  9. thomco80

    thomco80 Rookie

    Apr 7, 2021
    Full Name:
    Tomas Szemes
    Thanks guys for help, found it. The button was the problem. Some messed up repair was made (see picture). Can't see how this "repair" could ever have worked, the central part never gets into contact with the wired outer metal circle. The horn works fine when wired, I need to figure out my own fix.

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