Like just about any feature on a vehicle, a horn can require replacement over time. Whether it needs to be replaced or you simply prefer one with a new sound, a horn is easily changed. The Nissan Altima is built so that the horn can be replaced by an owner. Once you get a compatible horn kit, you can remove the old horn and install the new one in a matter of minutes.
Purchase a horn kit that is compatible with the Altima.
Find the Altima's original horn located under the hood, directly behind the grill.
Detach the power connector from the horn by removing out the mounting bolt using a socket wrench. Detach the wiring harness and remove the mounting bolt by turning it counterclockwise with the socket wrench
Remove the horn. Mount the new horn in the same location. Tighten the mounting bolt by turning it clockwise with a socket wrench.
Attach the wiring harness to the new horn and close the hood. Test the new horn to ensure it is working properly.
