Eureka! pulled horn button assembly off steering wheel yesterday and the wire inside was badly frayed and grounding out. Replaced wire, added new connectors with heat shrink crimp casings, reconnected ends and voilla, horn works great now! Had some 90w gear oil leak out of the bottom hole where the wire exits the steering column under the truck when I removed the rubber plug that holds the wire in place on bottom of steering box. Cracked open the fill nut on top of the steering box and it looks completely dry. TM says it takes 3 1/8 pints of 90w gear oil. Will be taking drain plug out to see if anything is left, will drain and refill. Replacing horn wire took all of about 30 minutes total, much easier than anticipated. Hopefully leak is not too bad, I do not look forward to taking steering box apart to replace seals/gaskets. I have heard horror stories about this.