What sets the Prius apart from other economy cars is its mode of power. In addition to a four-cylinder gasoline engine, the Prius has an electric motor. And unlike electric cars that must be plugged in to have their batteries recharged, the gasoline engine recharges the Prius' system while driving. The switch from electric to gasoline power is seamless and done automatically. Since the Prius is a small car that may be overlooked by larger vehicles while on the highway, many Prius owners choose to replace their stock horns with louder aftermarket units easily heard by other drivers.
Open the hood. Locate the two bolts and 10 snap fasteners that attach the front fascia panel (which is actually the upper part of the front bumper cover) to the radiator support cross member. Remove the bolts with an adjustable wrench turned in a counterclockwise direction and place them aside. Pry up carefully on the snap fasteners with a flat-blade screwdriver.
Locate the stock Prius horns by pulling back the top of the fascia panel and looking down. (The horns are bolted to the from the radiator support below the top of the fascia.) Pull the wiring connector from the horn you wish to replace by pulling it straight off of the plastic terminal on the horn.
Remove the horn from the car by loosening and removing the holding bolt from the horn's mounting bracket in a counter-clockwise direction with an adjustable wrench. Remove the horn from the vehicle.
Check the directions on the new horn for its amperage rating, as the stock units use a 10-amp fuse. Make sure the replacement horn does not draw more than 10 amps.
Place the hole in the replacement horn's mounting bracket over the stock horn mounting hole in the radiator support. Thread the original holding bolt into the hole and tighten it with an adjustable wrench in a clockwise direction.
Make sure the opening in the horn is facing downward so water can drain out. Make sure the horn is not touching any other of your car's components Loosen the mounting bolt and make adjustments if necessary. Push the wiring plug into the horn's connector until it is fully seated.
Push the front fascia back into place and push the snap fasteners into their mounting holes until they click into place. Replace the two holding bolts with an adjustable wrench turned in a clockwise direction. Close the hood.
