When electrical items on the rear tailgate of a wagon are not working correctly, among the normal bulb / fuse checks, take a look at the wiring harness that is routed through the tailgate hinges. You can view it from in back of the wagon and looking down on the upper hinges. Very common for these wire harnesses to crack in this cavity. Also verify ground that is located in same area. Several good fix it ideas in the archives.

240 Horns are known for short lives. check the voltage and resistance at the horn when steering wheel horn button is pushed in. Check at the horn plug in. That will let you know which direction to proceed.