Rep Power: 0

Horn quit, found the blown fuse which also prevents the Stop lights from working. Replaced the fuse and it blew immediately, is there an easy way to find the short in the system?

 
Rep Power: 229

Any aftermarket parts equipped to the car? and if not, since the tail lights don't move and are positioned inside the car, I would check the wires around the horn. Also try to remember when the horn stopped work as you be able to remember what you have done to the circuit. just keep the fuse rating the same, it is written on the fuse panel cover.

 
Rep Power: 812

check the actual horn (under the bumper near the washer fluid tank), it must have a good ground connection to the car body for it to function properly.

 
Rep Power: 308

The wiring to the horn itself would only have voltage present when using the horn. I'm guessing the brake circuit or a line with constant power at least.

Use a bulb in place of the fuse... It will glow bright as long as the short is present. Locate and repair the short and the bulb will go out or very dim and the fuse can then be replaced.