I have a 1988 F150 with 5.0L engine, 2WD, AOD transmission, and cruise control.

My horn and cruise control both have stopped working, and I've discovered that a two-way and possibly a three-way short has occurred between the heavy-gauge sheet metal cone and the two non-ground connectors under the steering wheel cover. I've examined the wiring diagram in the Haynes manual, and it looks like I need to do some diagnostics involving the horn relay and the cruise control amplifier. Does anyone know where these two things are located?

 

Sounds more like a bad clockspring (technically a "sliding contact" ) under the steering wheel.

 

Usually behind the instrument cluster, or above the gas pedal. Read this caption:

 

The problem was that the slip-ring contacts on the turn-signal/hazard multi-function switch assembly were broken -- most likely because of excessive wear and binding on the copper contact heads. Replacing that switch and cleaning and fine-sanding and very slightly lubing the slip rings with tune-up grease solved the problem. The Haynes manual directions for the replacement had me worried until I discovered that the very red wedge in the connector was easy to remove in order to push aside the terminal holding clips (but this procedure did not match the Haynes manual directions, which would have required a special tool). The new switch cost nearly $100 from a Ford dealer, but I now have cruise control and a horn.

Wish my erratic EGR various diagnostic codes and occasional MIL flashing were as easy and straightforward to diagnose and repair.