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  • Odd 12V boat horn problem

    I'm experiencing an odd problem with a boat horn, and although this forum is generally for household electrician problems, I'm hoping the collective knowledge can help me out.

    I bought a new 12V horn which draws 2 amps, and tested it by bridging the negative and positive under the dash. When I installed it, all it made was a meek clicking sound as if it wasn't getting enough power. I checked the voltage and it read 12.3 volts. I swapped the negative and positive thinking it may be sensitive to polarity, and that didn't fix it. I even bypassed the fuses, even though they were good, no change. There is no relay, just a normally off pushbutton switch (rated for 20A IIRC). My next step is to verify the horn itself by removing and testing directly on the battery posts.

    I don't know a lot about DC, but could it be that the wiring cannot support the amperage draw? So even though I read 12.3 volts, maybe only a couple strands are actually conducting?

    Thanks.

    edit: I ask about the wiring because it is old and some of the wires are "crunchy" which I suppose is the copper conductors oxidizing.
    Last edited by JoePolvino; 06-03-2013, 09:02 AM. Reason: eta

  • #2
    Re: Odd 12V boat horn problem

    probably the wiring, but could also be debris inside the horn assembly. we had this problem on our boat when bees built nests inside. a simple champagne cork solved that problem when we stored the boat.
    ~~

    ... it was plumbed by Ray Charles and his helper Stevie Wonder

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    • #3
      Re: Odd 12V boat horn problem

      I do not know what is done to day, but in years past cars used horn relays, (I am sure they still do but have not had to work on the newer units) the switch only ran ran the relay and the relay was nearly battery direct to horn.

      some info and diagram.
      Automobile Electrical Systems - Conclusion

      depending on what your wiring is going through, one may try a heaver duty switch,

      I would most likely consider a relay for a pre 80 vehicle as they would most likely fire wall mount and use screws to wire to, and not take a holder,

      some thing like this,
      http://www.amazon.com/ACDelco-U1738-...rds=Horn+Relay

      there is a diagram that should work for the three terminal unit, on a three terminal I am guessing the case needs to be grounded,
      http://www.team-bhp.com/forum/modifi...-horns-34.html
      Last edited by BHD; 06-03-2013, 10:13 AM.
      Push sticks/blocks Save Fingers
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      • #4
        Re: Odd 12V boat horn problem

        New horn; so corrosion and bee nests should not be a problem.

        "....but could it be that the wiring cannot support the amperage draw?" Bingo, It is likely the wiring can not carry the amperage necessary for the horn. First test it across the battery terminals to be sure it works. Then test the voltage at the horn with the horn installed in the circuit. (I'm betting its much less than 12v) BTW, it should be about 13.5v with the motor running.

        It may be necessary to replace the wiring with new or search for a bad connection. Also try bypassing the horn switch.

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        • #5
          Re: Odd 12V boat horn problem

          Originally posted by johncameron View Post
          New horn; so corrosion and bee nests should not be a problem.

          "....but could it be that the wiring cannot support the amperage draw?" Bingo, It is likely the wiring can not carry the amperage necessary for the horn. First test it across the battery terminals to be sure it works. Then test the voltage at the horn with the horn installed in the circuit. (I'm betting its much less than 12v) BTW, it should be about 13.5v with the motor running.

          It may be necessary to replace the wiring with new or search for a bad connection. Also try bypassing the horn switch.
          Thanks, once I got it installed and it started not working, I did bypass the horn switch. Still got clicking sound. This was from the main ground buss wired directly to the battery and a hot wire directly from the battery that goes to a small bank of fuses; I tried both "sides" of the hot bank, fused and un-fused. I think I'll try this next:
          1. Verify horn works directly on battery.
          2. Run a cheater ground wire from the battery to the horn, and the other side to the positive fuse bank. If it works, replace ground wire.
          3. Run a cheater positive wire from the battery to the horn, and the other side to the ground buss. If it works, replace positive wire.
          4. If neither above work, maybe both ground and hot leading from battery are bad and need to be replaced. I can figure this out with 2 cheater wires.

          This might also save me $30 because my fuel sender is not registering any level to the fuel gauge!

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          • #6
            Re: Horn diaphragm contacts need adjustment?

            Is there a screw which adjusts the contact closer to or away from the diaphragm contact?
            I would turn it counterclockwise to back the contact away from the diaphragm. Then apply current and slowly turn clockwise and find the ideal volume.

            Their supplied switch should be more than adequate for the 2-amp load.
            I'd take an educated guess - but I'm unqualified.
            It ain't just soot, it's paydirt.
            "I swear, wherever Gift goes, argument follows." -Youtube comment

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            • #7
              Re: Horn diaphragm contacts need adjustment?

              I figured it out. Got an early start, cheated the ground, and the horn worked.

              Turned out the ground from the battery had 3 taps (stern light, bilge, fuel sender) and they were all corroded. Also, I pulled gently on the fuel sender wire which goes under the decking and it wasn't connected to anything! Cheated negative to the post on the sender and I was getting a fuel level reading for the first time in 2 years.

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              • #8
                Re: Horn diaphragm contacts need adjustment?

                I've found when dealing with anything electrical on ANY kind of 12V systems (boats, trailers, tractors, cars, trucks, etc.), the culprit is most times with a grounding issue. The problem then becomes where, which can sometimes be easy, sometimes hard.


                Ron


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