1993 ford probe 2.0L
the horn, does not work, could it be a relay or fuse. or something else?
If it is a relay where is it?

 

Just use your middle finger instead

 

There should be a 20A fuse in the passenger compartment fuse panel that feeds the horn relay. That should be checked first.

The relay itself is in the power distribution box under the hood. However, before you condemn the relay you ought to check the connectors and grounds at the horns (there are two horns). By using a mulitmeter or simple test lamp you can check whether 12v is making it out to the horns when the horn button is pressed. (The horns themselves are kinda tucked into the driver's side front fender, accessible from underneath the car I believe.)

If you get 12v, then you know the problem is the horns or their connectors and/or grounds. If no 12v, then that would seem to confirm a problem with the relay.

The horns are grounded through their mounting bolts and brackets, so you should check for moisture and corroison there, as well. (Since you're working in the area anyway, it's a good idea to remove the horns and use a wire brush on the mounting surfaces).

If the horns are shot, you can get OEM replacements at most parts stores, usually right off the shelf.