Use a simple fused jumper to pinpoint the problem with a bad horn. Often the fix is simple and cheap.
Make a fused jumper with 16-gauge wire, two clamps and an in-line fuse holder. Connect one clamp to the terminal on the horn and quickly touch the other end to the positive battery terminal.
Vehicle horns sit up front where they’re exposed to rain and road chemicals. Once that spray gets into the horn’s innards, it can short out the coil and kill the horn (and blow the fuse in the process). But an inoperative horn can also be caused by a bad horn switch in your steering wheel, a broken “clock spring” under the steering wheel, a bum horn relay, a broken wire or a corroded ground. Here’s how to check the most likely suspects.
Start with the fuse. Refer to the owner’s manual for its location. If the fuse is good, jump power directly to the horn with a homemade fused jumper (photo). If the fuse blows, you’ve got a bum horn. If the horn makes a clicking sound, the problem could be a poor ground connection. Clean the horn’s ground connection and try powering the horn again. If the horn still clicks, you’ll have to replace it.
Search the fuse box for the horn relay and then find another one with the same part number to swap with it. If the horn works, buy a new relay.
If the horn works with jumpered power, the problem lies upstream. Before you waste time searching for a broken wire, try swapping out the horn relay (photo). If the relay works, you’re looking at a much bigger problem. Take it to a pro.