Mine went bad, as well. I bought an Ah-ooga horn to put in. I finally located the horn, but am scratching my head over replacing it. Basically, it's just behind and below the left headlight (from the driver's seat), in the bumper cavity. It looks like quite a bit of stuff will have to be removed just to get to it. Not sure I want to tackle it.
horn circuit mazda bt 50
The horn for the Mazda 3 is located below the drivers side headlight. The easiest way to reach it is by taking off the plastic piece on the bottomside of the vehicle. The horn will be mounted on a bracket. The single wire connected to the horn is power, the bracket is ground.
horns are usually located near the grill area in front of the car.
its located behind the front bumper by the passenger side headlight
Have your Mazda dealer parts department print out a picture of the relays location for you. They will do this if you ask them.
Replace it.
The horn relay should be located on the fuse box under the dash. most of the horn relay's that I have seen are a big white fuse, if it isn't on the fuse box, check near the horn.
Open the hood, look at the front portion about where the bumper is, a horn bell is mounted there, get a new one and wire it up
Open hood and disconnect the wire from the horn itself located under right front fender.
ollie Collins2 horns behind the front bumper
The horn is located on the passenger side of the radiator support behind the bumper. The horn relay is located on the passenger side fenderwell. I've attached some links below for future reference.
The horn is located on the front passenger side of the car. if you remove the front passenger headlight you will be able to see it from there