Air Horn Installation in a '94 Miata

I recently installed air horns in my '94 Miata and I thought that others might be interested in the procedures that I used. The manufacturer of the horns presents generalized instructions, but it's difficult to accomplish them without some creativity.

This page is merely informative and is intended to relate my adventures and methodology in installing this item. If your mechanical skills and background are limited, you should get a mechanic to do the installation of this item. Be advised that if you copy any of my methods or procedures, you're doing this at your own risk. Horns are very important pieces of safety equipment and a malfunctioning horn might cause serious injury or death. Also faults in the electric hookup might cause damage or fires.

Note - several important words of advice from the manufacturer. Make sure the primary power circuit is fuse protected. And be sure to use a power relay, since the air-compressor will draw up to 20 amps and the horn is on the same circuit as the brake lights.

Oh yes, LEFT clicking a thumbnail pix will bring up a much larger pix. RIGHT clicking on either pix will save the pix to your PC.

• Succinctly, this install consists of five steps:
• Preassembling and wiring the compressor and relay on a bracket; and the two horns on a second bracket.
• Installing and tieing off a fused 12 volt power tap wire.
• Bolting the dual-horn bracket on a pre-existing bolt.
• Removing the original equipment Miata-horn bracket and bolting the relay/compressor assembly in its place.
• Connecting the 12volt power and horn wire to the relay; and the plastic air hose to the compressor.

• Work that I did in my house.
• I first needed to preassemble two brackets before going out to my car. ie.
  • I purchased a three inch Tee plate from my local hardware store - cabinets section. see fig-01
  • An eleven inch metal strap/bracket for the horns was fabricated from metal scrap. This bracket was about eleven inches by one inch by 1/8 inch with three holes drilled and a 45 degree bite off one corner (hacksaw) for clearances. see fig 5, 6, 7
• I mounted the relay and compressor on the Tee (fig 2,3,4) and prewired them together. On my installation
  • The compressor (plus) lug connected to relay lug # 87
  • The compressor (minus) lug connected to ground
  • Relay lug # 86 connected to ground

  After wiring the compressor and relay together, two terminals on the relay were still unconnected. One of these terminals was for the twelve volt power and the other was for the factory horn connector. Your relay and compressor hookup may be different than mine so refer to the horn manufacturer's hookup instructions rather than blindly copying my hookup in the pictures. If you install this or any other device in your car, I urge you to use electric cable ties, washers and lockwashers liberally.

• The two horns were mounted on the 11" strap as shown in fig 5, 6, 7. I found that Vaseline made it easier to slip on the plastic tubing.

• Work that I did in my car.
• First I removed the four foot wide rubber shield (4 plastic bolts and 4 pull-out bolt sockets) to expose the original horn and bracket.
• I next ran a 12 volt power wire (about 6 ft of 12 gage) from the fusebox 30amp fuse (see fig 8, 9) to the neighborhood of the original horn and tied it off. Both ends of this wire got female solderless push-on connectors. Additionaly the quick disconnect connector at the fuse box end got a fuse power tap pushed into it. This power tap fits around one of the prongs of the 30amp headlamp motor fuse (see fig 8, 9) and then the fuse is reinserted in the fuse holder. Both connectors and the fuse power tap may be purchased at a local auto parts store (see fig 12). Initially I guessed wrong on which lug of the fuse to tap. Later I checked with a voltmeter and corrected my mistake. The other end on this power wire will plug into one lug (lug number 30 on my relay) of the horn power relay. I used cable ties liberally and tried to route this wire neatly while avoiding sharp metal edges that might cut through the wire insulation.
• The horn assembly (two horns, a bracket, and tubing) was mounted on the 10mm nut to the right of the latch. I removed my decorative radiator grill and installed the air horn assembly through the bottom opening. Now you can see why one corner of the strap was cut off for clearance. see fig 10. Initially I failed to properly adjust the horn clearances and was puzzled by a new rattle, but that was easy to fix.
• Now I removed the original horn and bracket (one 10mm bolt) and disconnected the factory horn electric wire connector (I had some difficulty with this connector until I discovered that Mazda had put a lock button on the connector). The built-up relay/compressor assembly was to be installed where the factory horn had been. The relay/compressor 3 inch Tee was fastened to the original horn bracket hole using the original bolt (see fig-11). I then slipped the horn plastic tubing onto the compressor spigot fitting and connected both the 12volt power connector and the factory horn wire to the relay (On my relay, 12 volts went to lug # 30 and the horn wire to lug # 85). Small hands are a blessing here. It is possible to install this assembly from the top, but coming up from the radiator mouth is much easier.
• That was it!! Except for replacing the four foot rubber shield and the testing, I was done.

A coworker, seeing an early version of this page, suggested that there may be an empty fuse socket that can be used. Then it would not be necessary to share the 30amp headlamp motor fuse with the air horns. I didn't check this out however. The electric horn manufacturer also suggests using a toggle switch so that either the air horns or the factory horn could be used. I didn't implement this suggestion either.

Fig-01 Fig-02 Fig-03 Fig-04
Fig-05 Fig-06 Fig-07 Fig-08
Fig-09 Fig-10 Fig-11 Fig-12