Replacing the stock horn

:Nissan Leaf
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Information

Replace the stock horn with aftermarket horns for a more… authoritative, horn sound. For example, PIAA 500Hz/600Hz electric horns, Fiamm El Grande Twin Horns, or Stebel Nautilus Compact Motorcycle Air Horn (115 dB on 12V).
(The VSP (Vehicles Sound for Pedestrians) warning and the alarm’s arm “beep” does not use the horn, so upgrading the horn do not affect those sounds. Some people wire their alarm horn output to the upgraded horn.)

The stock horn is on a 10A fuse and is already controlled by a relay. The Fiamm El Grande horns draws 10A, so it can be simply swapped with the stock horn. However, horns such as the Stebel Nautilus/Nautilus Compact draws more amps (18A in case of the Nautilus’s), so adding a relay as well as larger gauge wire, with an aftermarket wiring kit, for example, ensures that the aftermarket horn can draw enough current to produce its full sound volume. Both the horn fuse and the horn relay are in the black fuse box in front of the 12V battery.
Note that the Stebel Nautilus’ installation instructions call for installing the horn within 15° of vertical, otherwise you might get only one tone from the horn instead of two.

How-To

(NOTE: Here is the main “horn upgrade” post in the forums.)
The stock horn has two male 1/4″ spade connectors, which connect to two corresponding female connectors from the wiring harness. One female connector, on the long wire from the wiring harness, is the negative lead; the other female connector, on the shorter wire, is the positive lead. (The female connectors have a nub that you need to squeeze to disconnect.)
If your new horns come as a pair, connect them in parallel: connect their positive terminals together and then to the positive lead (shorter wire from wiring harness); connect their negative terminals together and then to the negative lead (longer wire from wiring harness). This means that, for Fiamm El Grande horns, you need two ‘Y’ leads. Each lead has one male spade connector to two female spade connectors:

The Fiamm horns’ mounting bolt is also its negative terminal. The kit should include washers that has a spade connector on their perimeter; the washer goes on the bolt and its spade connector provides the negative contact point. The single male spade connector on the horn’s body is its positive terminal.
The horn bracket’s bolt is 12mm; it is torqued to 13 ft-lbs.
An alternate method of mounting is to mount the horns to one side Interwiki: mnl++, so as to minimize blockage of air flow through the radiator.

Use self-tapping screws and mount the horn(s) to the aluminum impact absorber in the bumper. The aluminum impact absorber appears to be sufficiently grounded to not require a connection to ground.

Method 1: From Underneath

(This is the preferred method for 2014 LEAF’s.)
Remove the forward underbody panel to get at the horn:

Forward underbody panel

Forward underbody panel, removed Interwiki: mnl++

Forward underbody panel, fasteners Interwiki: mnl++

Horn Interwiki: mnl++

Method 2: From Above

Alternatively, for LEAFs before 2013 model year you can replace the horn from above.
This involves removing the radiator’s cowl and the coolant expansion tank.

Updated on October 12, 2018

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