Why is my 2015 Subaru Outback horn not working?

If Your 2015 Subaru Outback horn is not working it's usually the horn relay. The horn relay serves as the relay that controls power to the vehicle's horn. When current is applied to the relay, the horn's power circuit is completed, allowing the horn to function and ring. When the relay fails it can leave the vehicle without a functioning horn. To provide the most power, and thus get the most noise, You can wire a relay to power Your horn. The relay uses a small amount of power (the original switch circuit) to turn on and off a bigger amount of power (the new heavier wire) to the horn.