How to Wire an Aftermarket Air Horn Relay

Upgrading to an aftermarket air horn can greatly enhance your vehicle’s sound, making it louder and more attention-grabbing. To ensure it works effectively, you need to wire the air horn with a relay, which helps manage the high current required to power the horn. This step-by-step guide will help you wire the air horn relay with safety and accuracy, ensuring your installation goes smoothly.

Tools and Materials Needed

Before beginning the wiring process, gather the following tools and materials:

• Air horn kit with relay – Includes the horns, relay, fuse, and necessary wiring.
• Electrical connectors – Butt connectors, spade connectors, and ring terminals.
• 14-16 gauge wire – Strong enough to handle the current needed for the air horn.
• Inline fuse holder – To protect the circuit from overcurrent or short circuits.
• Horn switch – To activate the air horn (if your kit doesn’t include one).
• Hand tools – Wire cutters, crimping tool, screwdrivers, and a multimeter for testing.
• Electrical tape and zip ties – For insulation and securing wires.

Understanding the Relay: Key Components

The relay is an essential part of the air horn installation, as it switches the high-current circuit needed to power the horn, triggered by a low-voltage signal from your horn switch. Understanding the relay’s components will ensure that you make the correct connections.

• Terminal 30 (Common): This is where you’ll connect the power source (usually from the battery).
• Terminal 87 (Normally Open): This terminal powers the air horn when the relay is activated.
• Terminal 85 (Coil Ground): Connects to the vehicle’s ground.
• Terminal 86 (Coil Power): This is the terminal that receives power when the horn switch is activated.

Step-by-Step Guide to Wiring an Aftermarket Air Horn Relay

Step 1: Disconnect the Vehicle Battery

Safety first! Always disconnect the negative terminal of the battery before working on your vehicle’s electrical system. This will protect you from electrical shocks and prevent accidental short circuits.

Step 2: Connect Power to Terminal 30

Run a wire from the positive terminal of the battery or a fuse block (preferably 12V) to Terminal 30 on the relay. This wire should be at least 14 gauge to handle the high current required by the air horn. If you’re using a fuse block, ensure that it is rated for at least 30-40 amps, depending on the air horn’s requirements.

Tip: If connecting directly to the battery, place an inline fuse between the battery and the relay to prevent overcurrent situations.

Step 3: Wire the Air Horn to Terminal 87

Next, connect Terminal 87 on the relay to the positive terminal of your air horn. If your kit includes multiple horns, ensure that the relay can handle the total amperage of the horns. For a two-horn setup, this will likely require a relay rated for higher amperage.

Step 4: Ground the Air Horns

For the air horn to function properly, it must be grounded. Connect the negative terminal of the horn(s) to the vehicle’s chassis or a solid ground point. A poor or unreliable ground connection can cause intermittent horn issues.

Step 5: Connect the Horn Switch to Terminal 86

Now, run a wire from the horn switch to Terminal 86 on the relay. This switch activates the relay, which in turn powers the horn. You can wire the switch to the vehicle’s ignition circuit or use a manual switch. Ensure the switch is rated for 12V DC operation.

Step 6: Ground the Relay at Terminal 85

Connect Terminal 85 to the vehicle’s ground. This will complete the relay’s circuit, ensuring it works when the horn switch is triggered.

Step 7: Install the Inline Fuse

Install an inline fuse between the positive battery terminal and Terminal 30 of the relay. The fuse should be rated for 30-40 amps, depending on your air horn kit. Place the fuse as close to the battery as possible to ensure the protection of the circuit.

Step 8: Testing the System

Once everything is wired, reconnect the vehicle’s battery. Turn on the ignition and activate the horn switch. If everything is connected correctly, the relay should click, and the air horn should sound off. If the horn doesn’t work, double-check the fuse, wiring connections, and grounding points.

Step 9: Secure and Insulate Wires

Use zip ties or electrical tape to secure the wires and prevent them from getting tangled or damaged. Insulate any exposed wiring, especially where it may come into contact with metal parts of the vehicle, to prevent shorts.

Troubleshooting Tips

If you encounter issues, here are a few troubleshooting steps to help resolve common problems:

• Horn not sounding? Check the power connections at Terminal 30 and Terminal 87, and ensure the relay is grounded properly.
• Relay clicking but horn not working? Verify the air horn’s ground connection and check for any issues with the horn itself.
• Fuse keeps blowing? Ensure the fuse rating matches the air horn’s power requirements. If you’re using a higher-power air horn, you may need to use a relay with a higher amperage rating.
• Low sound or weak tone? Check for low voltage or insufficient power from the battery. Sometimes, the air horn may not function properly if the battery voltage is low.

Additional Tips and Recommendations

• Use Heavy Duty Relays: Air horns can draw a lot of current. Make sure the relay is rated high enough for your horn’s power requirements to prevent overheating and potential damage.
• Wire Sizing: Using wire that’s too small for the current draw of the air horn can cause voltage drops or overheating. Stick to 14-16 gauge wire for most air horns.
• Grounding: A poor ground connection is one of the most common causes of electrical issues with air horns. Ensure all ground connections are solid and free of rust or paint.

Conclusion: Your Aftermarket Air Horn is Ready to Go!

Wiring an aftermarket air horn relay is a simple but crucial task that can make a big difference in the performance of your horn. By following these steps carefully and ensuring all connections are secure and insulated, you’ll have your air horn working in no time. With the added safety of a properly fused and grounded circuit, your vehicle will be ready to make some noise!