My horns would blow constantly so I pulled out the book, ran through the diagnostics - remove the relay and jumped across terminals #1 and #2 with a test light. The light stayed on indicating a dead short or bad switch (horn button.) I removed the horn pad and disassembled it to find the foam insulation that separated the horn contacts had deteriorated and was allowing the contacts to touch, blowing the horn.
If you can find a new horn pad they are upwards of $150. So I decided to see if I could replace the foam insulators. Here's how to do it, in some detail. This is not step by step but you'll be able to fill in the gaps when you see how it's put together.
Remove the horn pad by removing the 2 screws on the back of the steering wheel - use a thin wall nut driver.
Disassemble the horn pad - remove the plastic cover, remove 4 small silver screws that hold the center pad in place. Unplug the wires to the side buttons and center button. Separate the contacts by pushing the male wire contacts through the pad frame. I used some home weatherstripping found at Home Depot and cut it to the triangular size of the deteriorated insulation. Punch out the 3 holes using a paper hole punch and cut small slits to allow the wire contact to slide through. The weatherstripping has a paper side (this would be removed to reveal the adhesive when insulating a home window but leave it on for this application.) When inserting the new insulation onto the contact place that paper side toward the 3 raised contacts- the contacts should show through the 3 holes. Reassemble the unit then check for continuity from the spring loaded wire to the longer grounding contacts on the side buttons (these sit just below the contacts the wires attach to and rest against the grounding bar on the steering wheel). If you have continuity without the buttons being pushed the contacts in the buttons are still touching. If not, you're good.
I've done my best to describe this process but may have failed. If so, please contact me and I'll walk you through it. Good luck.

 

Nice work and nice write-up. Thanks.

 

Nice job... I'll have to save a copy of the write up for future use...