Car Fix DIY Videos

Overview of the Infiniti G35 Horn System

The Infiniti G35, whether coupe or sedan (produced between 2003–2007), comes equipped with a dual horn setup—one high-tone and one low-tone horn. These are mounted in front of the radiator support or behind the front bumper, depending on the model year and trim. The horns are powered by a 12-volt circuit that is activated by the horn switch on the steering wheel. When pressed, the switch completes a circuit through the horn relay and sends current to the horns.

If you’re experiencing horn issues or simply want a louder, more aggressive tone, replacing or upgrading the horns is a common DIY project. This process, however, involves more than just swapping out the units—you need to ensure compatibility with the electrical system and proper mounting.

Accessing the Factory Horns

To access the horns on a G35:

Front Bumper Removal (sometimes required): On many G35 models, especially the coupe, accessing the horn requires removing or loosening the front bumper cover. This is done by:

Removing plastic clips along the top edge (under the hood).

Removing screws and fasteners in the wheel wells and underneath the bumper.

Gently pulling the bumper cover forward.

Alternative Method (for some sedans): The horns may be accessible by removing the front grille or reaching from beneath the car after removing the splash shield.

Once the horns are accessible, locate both the high-tone and low-tone horns, usually mounted to the radiator support. Each horn will have a power wire (and may ground through its mounting bracket or a separate ground wire).

Removing the Original Horns

To remove the OEM horns:

Unplug the electrical connector from each horn.

Use a socket or wrench to remove the bolt that secures each horn to the mounting bracket or radiator support.

Inspect the wiring for any corrosion, damage, or fraying.

If you’re reusing the same wires for a new horn, be sure they’re clean and have solid terminal connections.

Installing a Replacement or Aftermarket Horn

OEM Replacement:

If you’re replacing the horn with the same OEM or similar unit, simply mount the new horn in the original position using the factory hardware.

Plug in the connector or splice in the wires using crimp connectors or solder.

Be sure the bracket is grounded (if it serves as the ground path).

Aftermarket Horns:
Installing an aftermarket horn such as a Hella Supertone, Wolo, or Fiamm unit may require:

Mounting Considerations: Most aftermarket horns come with a universal L-bracket. Find a spot on the frame or radiator support that allows proper sound projection and doesn’t obstruct other components. Use existing bolt holes when possible.

Electrical Connection: Aftermarket horns often require a ground and a positive terminal. Use a ring terminal to secure the ground to a clean metal surface on the chassis.

Using a Relay: Louder horns typically draw more amperage than the OEM system can handle. In this case:

Use a 30/40 amp relay.

Connect pin 30 to a fused 12V source (battery or accessory).

Pin 85 goes to the horn switch wire (original horn wire).

Pin 86 goes to ground.

Pin 87 goes to the new horn’s positive terminal.

Ground the horn’s negative terminal to the chassis.

This setup protects your factory wiring and ensures consistent horn performance.

Troubleshooting After Installation

If your horn isn’t working after the replacement, consider the following checks:

Check the Fuse:

The G35 horn circuit uses a 10A or 15A fuse located in the fuse box under the hood (IPDM).

Refer to your owner’s manual or fuse box diagram to locate it.

If blown, replace it with a fuse of the same amperage.

Check the Relay:

The horn relay may have failed or not be properly engaging.

Swap it with another identical relay from the fuse box (like the A/C or fog light relay) to test.

If the horn works with the swapped relay, replace the old one.

Horn Switch (Steering Wheel Button):

If pressing the horn does nothing and you’ve confirmed the horn itself works, the issue may lie in the horn switch or clock spring.

The clock spring is a spiral-wound electrical connector inside the steering wheel that allows the horn, airbag, and audio controls to function while the wheel turns.

A broken or worn clock spring can cause intermittent or total failure of the horn switch.

Replacing it requires removing the airbag and steering wheel and should be done with caution.

Grounding Issues:

If the horn is mounted securely but doesn’t work, test the ground.

Use a multimeter to ensure you have continuity between the horn bracket and chassis ground.

Rust, paint, or corrosion can prevent proper grounding.

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