The clicking is the relay near the fuse panel. One is for the horn and the other for the battery saver. ( turns lights off ) So you know the horn button on wheel and the fuse is okay. Horn is very simple to change. I put mine up behind the headlight because it kept getting filled with water. The stock location isn't good. I've done mine twice in the past year.
The problem with the mounting is the horns have a little spiral like a seashell inside, and the mouth points down. Some of the water that gets shoved in when it rains, goes up over the top and is trapped against the metal diaphragm, which then rusts. I mounted mine pointed up, but drilled an 1/8" hole in the plastic body at the lowest spot when mounted to let the water out. It's only been about two years, but it's still working at the moment. I think I bought my horns from NAPA, they look the same and mount the same, but I had to change the lugs for the wiring weren't quite the same. Probably better to get them from Ford unless the price is way different between the two places.
When I recently discovered my horn had quit working i went through all the steps to test and make sure it was actually getting power. Once I determined that it was the horn that was faulty I removed it and bench tested again with an old battery and some alligator clips on the terminals and it still didn't work.
I went thru the process of shooting WD-40 into the horn opening and sloshing it around and still nothing.
A couple weeks had passed and the horn still sitting on the bench I decided to test it again by putting the power to it and still nothing.
The difference this time was I figured i had nothing to loose and tapped the side and back beside mounting bolt with a small piece of brass rod and it started to operate intermitenly, but not steady or very loud tho.
At that point still thinking i would be throwing in the garbage I decided to mess around with the adjustment screw that is factory covered with silicon and ended up removing it and shooting a little bit of WD-40 in the hole.
This is where things get interesting and remember that i still have the leads connected so the horn is getting power as i'm putting the ajdustment screw back in the horn begins to function but this time with a steady tone.
Now I simply adjust the screw til the horn seemed the loudest and put a new bloob of silicon on the head of the screw and reinstall the horn back on the car, push the horn pad and it seems to function as it should.
Just thought I'd pass on the info for anyone that wants to save a few bucks and feels like a little challange.
VERY common "fix" I did often on motorcycles. They get used so seldom, plus the change in stiffness of materials from age... re tuning them usually "fixes" them for quite a while in my past experience..
Most horns are that type if you look deep enough. Simply breaking the vibration setscrew loose can often get them working again, or cleaning up breaker point contacts to make them low resistance again. Water entry or rust usually the problem. I haven't bought a horn in 40 years, I always can fix them. I, like sailor learned long ago from motorcycle horns. Only reason to buy one is for when they cheap out and give you only one and adding the opposite tone then really ramps up the noise.
I wouldn't be spraying WD40 in there, once it hits current, the current will convert it to something (bubblegum) that does not help passage of that current. It's not electrical cleaner.
It's probably too late for this but you should know that Ford has a "secret recall" on the horns on the early Focuses. The NHTSA and Ford cut a deal on this - in exchange for replacing a failed horn no questions asked, NHTSA didn't require them to do a formal recall. There is a Ford TSB on this that specifies free horn replacement.
I went to my local library where they have an Alldata subscription and looked it up - sorry I didn't save the darn number. It was kind of irritating because I had just a week earlier replaced the horn on mine with one from a wrecker so I could have saved the $10 and gotten a new horn. :-(