Things You'll Need
Air horns are handheld or mounted devices commonly used on boats and large trucks. The horns use compressed air to create sound when the air is forced through a stanchion. The sound then travels through a large bell, which amplifies the sound. If the unit is not assembled correctly, sound may not come from the unit.
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Ensure the horn is mounted in an area where nothing obstructs the bell to prevent sound issues.
Remove the mounting screws of the horn, and inspect the mounting pad for signs of decay or wear if the horn is rattling the mounting area. Replace the mounting pad if necessary.
Refill the air canister if the gauge shows it is empty.
Check for kinked, split or bent hoses if the compressor is running, but there isn't any sound coming out. Secure all connections by tightening them with a wrench.
Check the connection on the compressor. The positive connection should lead to the relay and the negative to the ground. Switched connections will suck in air instead of blowing air out.
Remove the hoses from the horn by pulling them off the bib if the compressor is working but you are receiving no sound. Spray penetrating oil into the horn's air inlet to blow out dirt and debris. Reattach the hose and try the horn again.
Touch a volt connector to the positive and negative connection of the battery with the meter set to the X1 setting. Locate the voltage rating for the battery on the battery case, and compare the reading from the meter to the rating for the battery. If the reading is too high or low the battery needs replacing.