Installing a air horn in your car is an effective method of making yourself heard. Air horns consist of an air compressor that delivers air through tubing to a horn mounted under the hood. This system develops an ear-deafening tone that can be heard over long distances.
Open the bonnet and find the vehicle's stock horn. It is normally near the front of the engine bay. Honk the horn and listen for its location if it cannot be immediately spotted.
Use a 12-volt test light to determine the horn's live and neutral wires Attach the light's grounding clip to the vehicle's bare metal frame, and apply the probe to bare wire. The horn activates -- and the light illuminates -- when you touch the live wire.
Tap into the live wire's power using a scotch-lock connector. Place the vehicle's horn wire in one groove of the scotch-lock connector -- and some electrical wire in the other -- and close the latch. This forces a piece of metal into the wire, creating a connection.
Run the live wire along the chassis to the air horn's compressor. Strip and connect the inline fuse using a butt connector. Place the two, stripped wires in either end of the butt connector; compress the connector with pliers. Gently tug on the wires to assure a tight connection.
Connect the other side of the fuse wire to the positive terminal of the air compressor.
Connect a new section of electrical wire to the neutral wire at the vehicle's horn using the scotch-lock connector. Attach the neutral wire to the compressor's ground connection.
Install the correct-sized fuse into the fuse holder. This size of the needed fuse can be found in compressor manufacturer's manual.
Fasten any loose wires to the vehicle's chassis with cable ties. Wrap all of the connections in electrical tape to provide protection from the elements.
Air horns are potentially damaging to your hearing. Never honk the horn when someone is working near it.