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NB - Adding an air horn to existing stock horn

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  • NB - Adding an air horn to existing stock horn

    Hello All,

    I would like to add an air horn along with the existing stock horn. I get a used Fiamm 3000 serie air horn with additional 30 amp relay and fuse.

    has anyone have this setup or something similar to the following link ,

    http://themorans.org/themorans/timst...ns/NCHorns.htm

    Basically

    Relay #1) When the ignition is OFF, this sends power directly from the battery (not through the rest of the electrical system) to the stock meep-meep horn when the steering wheel horn button is pushed. This is the default state of the Miata horn.

    Relay #2) When the ignition is turned ON, the relay switches from the stock meep-meep horn to the trumpets which are then connected directly to the battery. The trumpets are "armed and ready" whenever the key is on.

    if yes will you give me an idea of how to wire them ?



    2002 LS Black Miata

  • #2
    His situation is different because his new horns are low-current electronic ones (8 amp fuse) so he doesn't have to upsize his fuse or wire gauge for the OEM horn. He can simply toggle between the OEM horn wiring and the new horn wiring off the same OEM wiring. I don't know why he went through the effort of adding 2 relays up front, seems unnecessary from my perspective, he probably only needed one new. You're talking about swapping your 15A fuse for a 30A fuse but maintaining existing wiring for the OEM horns. Technically your OEM wiring would not have sufficient overcurrent protection to prevent a fire from occurring if shorted. I would either suggest replacing the fuse and the relay and running new thicker-gauge wire to the OEM horn, or find an aftermarket horn that doesn't require upsizing your 15A fuse. Then it's easier to provide you a wiring diagram. Honestly, if your new FIAMM horn has a compressor, it's unlikely that the lock beep would be long enough in duration to run the compressor up to speed to make noise, so if you're worrying about waking neighbors you probably don't need to. If you just want to confirm you locked your car, the running lights will let you know.
    I can doodle up a circuit if you're still really interested. What year is your NB, that would be helpful info to add to your signature.
    EDIT: went ahead and sketched my idea out for you, assuming your horns use the OEM wiring.
    IMG_20200605_125309.jpg
    EDIT 2: here is wiring diagram for OEM horn circuit for a 2005
    Annotation 2020-06-05 125643.jpg
    Last edited by boatshoes; 06-05-2020, 03:02 PM.
    2001 BRG SE

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    • #3
      @boatshoes Thank you for your time and You make a very good point. I researched around and found another install which seems relatively straightforward

      https://www.miata.net/garage/air_horns.htm

      the wiring diagram is as follows,

      horn_relay_wiring_diagram.jpg
      The horn came with a 4 pin , 30 amp relay attached . so when compared to the above wiring , the relay has only one port for 87 .
      In this case what goes to port 85, is it the wire attached to the OEM horn ? .if so , the 87 connects to the (+) of the air horn compressor?

      Thanks again
      2002 LS Black Miata

      Comment


      • #4
        Ah so you are planning on keeping both. I think that's a fine idea. Original horn wire goes to 85, 86 grounds to the chassis. Power for new horns will flow from power bus through new 30A fuse, through new relay 30 to 87, through new horn. Rather than put the OEM horn on the new 30A circuit, I would do it like below. So you'll splice in a new wire to the relay coil from where the OEM horn connects up front. This makes it easily reversible. Then you'll run new heavy-gauge wire from the relay contact to the air horn.
        Annotation 2020-06-09 095426.jpg
        2001 BRG SE

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        • #5
          [QUOTE=boatshoes;367575]Ah so you are planning on keeping both. I think that's a fine idea. Original horn wire goes to 85, 86 grounds to the chassis. Power for new horns will flow from power bus through new 30A fuse, through new relay 30 to 87, through new horn. Rather than put the OEM horn on the new 30A circuit, I would do it like below. So you'll splice in a new wire to the relay coil from where the OEM horn connects up front. This makes it easily reversible. Then you'll run new heavy-gauge wire from the relay contact to the air horn.


          Thank you @boatshoes. I will give a try with your wiring diagram this week and let you know how it works out.
          2002 LS Black Miata

          Comment


          • #6
            @boatshoes
            Thank you for the detailed instructions. I was able to install the Fiamm horn keeping the existing horn and it worked as expected.
            Thank you again for your time and assistance.
            2002 LS Black Miata

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            • #7
              :clap:
              2001 BRG SE

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              • #8
                Originally posted by boatshoes View Post
                :clap:
                I want to know if this behavior is normal.
                the horn is working , however i was driving after dark last and noticed that whenever i press the horn, the headlights and tail lights dim .

                Thank you
                2002 LS Black Miata

                Comment


                • #9
                  With a big enough load, I think it would probably drag down the alternator a bit from 14v to 12v. Is it similar to if you rolled both windows up or down together? My headlights dim a bit when I'm moving the windows.
                  2001 BRG SE

                  Comment


                  • #10
                    Originally posted by boatshoes View Post
                    With a big enough load, I think it would probably drag down the alternator a bit from 14v to 12v. Is it similar to if you rolled both windows up or down together? My headlights dim a bit when I'm moving the windows.
                    I tested the lights last night again . The headlights dim a little more (like 50% more )when i use the horns when compared to the dim due to rolling up/down the windows together.

                    can it be due to having a thinner gauge wires for the new horn . the wires used for connecting the grounds are thin compared to the other wires(12 AWG).
                    2002 LS Black Miata

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