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Horn stuck on, removing relay/fuse doesn't help.

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  • Horn stuck on, removing relay/fuse doesn't help.

    I don't drive the car all that often but this morning I went to take it out for a lazy Sunday drive. It's been parked for maybe a month, with the battery disconnected. When I reconnected the battery the horn immediately started making noise (much to the frustration of my neighbors, I'm sure). Wiggling the steering wheel didn't help, removing the #7 fuse didn't help, and removing the K2 relay didn't help. I'm not really sure how the horn is still going with both the fuse and the relay removed, but it is. The only way to stop it is to disconnect the battery. The car is a 1990, was I looking at the wrong diagram and removing the wrong fuse?

    As far as I know, the car is completely stock. Is there any way for the horns to be going off with the fuse and relay removed, or am I probably dealing with hacked up wiring? I suppose my only solution might be to disconnect the horns and start tracing wires. Any suggestions before I do that?

    So much for my lazy Sunday drive...
    1990 BMW M3
    1989 Porsche 951
    1988 Volvo 240DL

  • #2
    are you sure its the vehicle horns and not a separate alarm system horns ,what you describe sound more like an alarm system horn sounding after battery disconnect. looking at the diagram for a 90 ,the only thing that would engage horn relay are the horn buttons, a short in the wiring between them or a problem in fuse block sending power to horns, ,and removing K2 or fuse 7 if wiring hasnt been modified should stop them like you tried . which again makes me wonder if its the correct horns (do you hear different horns if you connect batt and hit horn button with key on?). there is also a separate horn controlled by the OBC that might be going off if a code was set or the unit is failing.
    Angus Proud
    88 E30 M3 X2
    89 E30 325IX
    92 R100GS/PD
    :ha:

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    • #3
      It sure sounds like the vehicle horns. The alarm always trips immediately when reconnecting the battery. The siren shuts off as normal with the switch on the key fob, though the horn continues to sound.

      The sound is quite loud (as you'd expect from a car horn), however maybe it is that OBC horn. From your diagram it looks like pulling fuse 27 will cut power to that horn, correct? I'll try that, and also tapping the horn button in the car to see if it makes a different sound.

      Thanks for the help.
      1990 BMW M3
      1989 Porsche 951
      1988 Volvo 240DL

      Comment


      • #4
        If you have an alarm system, you may check if the horns are connected to the alarm via a separate relay. Start by unplugging the connectors from the horn one at a time, check for voltage as you connect the battery, then trace the wire upstream for splicing. Removing fuse 7 should disconnect the horns from the steering wheel so there might be another source that triggers them.

        GL

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        • #5
          Pulling fuse 27 stops the horn from sounding, as per spdracrm3'd suggestion.

          Except now I have an other question: If that horn sounding is indicative of a trouble code or a failing OBC, how to I go about troubleshooting it?
          1990 BMW M3
          1989 Porsche 951
          1988 Volvo 240DL

          Comment


          • #6
            well as you can see in the diagram the horn is controlled by a relay box (that is above and behind the ABS control unit behind drivers kick panel) ,,disconnect the C1 connector and check to see if pin 2 (brn/yellow) is providing a ground to the horn relay . if so its either a short in the wire to the OBC or the OBC is providing the ground (need to test this by disconnecting the OBC and see if ground to C1 pin 2 goes away ,if yes its inside the OBC ,if not theres a short to ground in wiring). if there is no ground on C1 pin 2 with it disconnected then the relay in the relay box is stuck on/bad or there is a problem inside the relay box . i would start by finding the relay box and disconnect it and inspect the pins (they are know to have issues causing no starts on the code side ) if connector and pins look ok reconnect it and see if horn stops blaring if it does then just moving the connector jiggled the relay enough for it to disengage ,if it still comes on start diagnosing the wiring and OBC as its proving the ground to turn horn relay on

            see pictures on last pages of ETM for component locations
            Angus Proud
            88 E30 M3 X2
            89 E30 325IX
            92 R100GS/PD
            :ha:

            Comment


            • #7
              Well I'm pleased to say this is "fixed." With fuse 27 pulled I could fiddle with things without losing my mind due to the noise. I can't see the screen on the OBC because (of course) the bulb is burned out, but based on what I read on http://www.e30zone.net/e30zonewiki/i...board_Computer I fiddled with, and apparently successfully reset the OBC. I re-inserted fuse 27, and the horn no longer sounds.

              I have no idea if this is fixed permanently. I suspect not, since I did nothing that I hadn't done a hundred times before, which leads me to believe something is starting to fail, but thanks to the help I've gotten here I at least know where to start troubleshooting if it happens again.
              1990 BMW M3
              1989 Porsche 951
              1988 Volvo 240DL

              Comment

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