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Car Horn sounds weak?

My car horn was working fine until a few days ago when it started to sound VERY soft. It STILL makes a sound mind you, but it sounds like someone is trying to pillow-smother a tiny cow. So then I connected it directly to the battery (with a fuse) and I nearly went deaf, so it’s not the horn itself–it honks loudly! Next, I changed around some relays of the same type in the fuse box but that didn’t do anything. What could the problem be?

Bad connection, bad relay, bad fuse. It depends on whether your car horn is directly controlled by the horn switch of if there’s a relay involved. If no relay, the problem is most likely the horn switch itself.

Sounds (heehee) like a bad ground.

Since the mounting hardware on horns creates the ground path for the circuit, and horns are usually on the radiator mounting structure or somewhere else subject to road contamination, corrosion of the hardware is common. The corrosion creates a high resistance connection. The resistance “drops” some of the voltage leaving less for the horn, and since a horn’s function is subject to the amount of voltage applied, the sound level drops.

Remove the horn, clean the mounting and its connections with wire brushes, and reinstall it… perhaps with a dielectric grease to inhibit corrosion.

my truck gets water in the horn somehow. I think…

a few minutes of honking seems to drive it out…

It’s unlikely to be water in the horn b/c it works ok if powered directly from the battery.

I agree with @insightful.

A bad ground where it mounts.

Because I do not know the year or condition of the vehicle, I’ll throw this one in too.
If it is mounted to the radiator support, check that the support is not rotted away to the point of not being a good ground. It could be hanging by a thread.


How did you connect the horn directly to the battery? If you ran a single lead from the positive battery terminal to the horn terminal with the horn in place, then I don’t see how it could be the ground. If you ran two leads from the battery, one from the negative terminal to the ground side of the horn and the other from the positive terminal to the terminal on the horn, then the ground is a suspect. Run a single lead from the negative terminal of the battery to the ground side of the horn and try pressing the horn button. If it honks with full volume, the problem is the ground. If it honks weakly, the switch, relay or wiring has a problem.