I purchased a very used 1988 F150 and the horn does not work (amoung other problems). Can someone tell me where the horn realy is located on that truck?

I've been reading on this and other threads, sounds like the place to look first is the horn realy. I've checked the fuses (good), and when I press the horn, I hear a clicking sound under the dash, but can't really get a good feel for where the realy might be.

Thanks.

 

The click is the relay, which suggests that it's working. Since the relay is powered by the same wire that powers the actual horn, I suspect either the horn is dead, or the wire (DB) between the relay & horn is cut. See if you have 12V at the horn with the button pressed.

Some trucks use a 3-terminal metal-housed relay (lower L of the pic) that's attached to the cruise control module; others use a plastic Ford-style relay under the middle of the dash near the gas pedal.