Locate the horn relay on 1985 rx 7 mazda - 1985 Mazda RX-7

SOURCE: 2002 Mazda Protege horn location

Their are usually in back of grille or on the underside of rails. you will need to take off the front bumper to get access.

SOURCE: 2003 Chevy Cavalier Horn Relay Location

under the dash in far left top corner iis a small panel inside are the flashers relays and buzzers which are difficult to remove and install.

SOURCE: 99 CAVALIER HORN RELAY LOCATION

If your horn isn't working and it isn't the horn itself the next thing to check is the horn wire in the steering wheel under the air bag. The little clip breaks off in time and the horn wire pops out. To repair you can remove the wheel and replace the part but I usually grind in a new notch in the old plastic and re attach the wire and it will work again.
Test the horn itself first. Just remove the connection to the horn and attach 2 wires to a live battery and tough the 2 sides of the contacts on the horn. If it blows the horn is good. If not replace the horn before you go any further.

SOURCE: Having horn problems on 2005 Mazda Tribute. The

Check the grounding source, also check if current flows to the horn wires, and its wire plugs are not corroded.

SOURCE: Fusbile Link-1983 Mazda RX-7

They are usually on the drivers side shock tower. And if you need them, and you want to buy them from me i have them,
Just let me know,
Robert