1999 Lincoln Town Car horn not working

To test your horn, you can run a wire directly from your battery positve post to your horn's wire terminal. (The horn is grounded to the body of the car thru the bolt attached to the horn bracket. It may just be the horn itself. As for the radio and clock, you can try unplugging the clock. Sometimes they go bad in the towncar and cause weird electrical problems. It is possible that your radio will again work if you unplug the clock. If there is no blown fuse then you may have to replace the clock. If this doesn't fix the radio then it may also just be shot.