Really, really bad
Well your not going to believe this but... one problem I have run into in my years of servicing Cavaliers. is a Bad ground where the horn mounts to the car. I have in the past have had to run a ground wire from the mounting point and drill a hole for another screw and ground the wire. Sounds crazy I know but have done this a couple of times and the horn then worked!
Sounds like the horn has a bad connection. I would replace the horn switch in the steering wheel.
Bad horn? Bad relay? Bad horn switch?
Normally if the problem is that you can't find the horn button the horn will not work at all. Considering that it only works at times but not always, you've probably got either a bad horn or a bad horn relay. If, however, your airbag light is also on, consider a bad clockspring coil. Also, this is a Dodge, so check for a corroded fusebox. See if wiggling fuses makes the horn work.
if the horn is already there and is bad, just disconnect the two wires on it, unscrew horn, remove it and reinstall the new one and reconnect the wires. If you don't have a horn, then find a suitable place under the hood and drill X number of holes. The switch is wired in series with the battery and horn. The button is placed at a convenient place you can get to it when you want to blow the horn.
bad ground or wiring, bad switch/button, bad horn, bad horn relay, fuse.
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Most likely a blown fuse. Otherwise bad wiring going to the horn or a bad horn.
Bad fuse.Bad horn button.Bad horn relay.Bad horn.Bad connections at any of these points, bad wiring between any of these points, or a bad ground.
Many times the horn itself could be bad; if you have power to the horn and no sound, replace the horn. I would get one from a salvage yard for $10-15. Roll down window. Hollar real loud "LOOK OUT!"
Bad horn unit - check to see if you are getting power to unit Bad horn relay? Blown fuse? Bad horn switch at steering wheel?
Could be a bad horn, bad relay or possible a bad horn ground. Try touching a wire straight from the battery (+) to the horn. If it sounds bad you need a new horn but if OK it's probably a dirty ground or bad relay. Try tightening the horn itself down a little to insure it's getting a good ground. Still sounds bad its probably the relay. Replace it. If none of this helps... a bad steering wheel switch maybe? Hope this helps.