[1crosscut]

I am currently fixing the same problem. What happend on mine was the small insulator piece at the end of the horn rod cracked allowing the soldered end of the wire to touch and ground against the side of the light switch housing.

You will need to unclip the wire bail that holds the light switch to the end of the steering collumn. This will allow you to pull the entire light switch housing away from the end of the collumn. At the end of the collumn you will then see a two pronged piece of metal that fits into slots in the light switch you just removed. That two pronged piece will have to be removed. To remove it have someone sit in the car and hold the light/horn switch from being pushed out while you push the two pronged piece up towards the steering box exposing a small c clip that you can remove with a needle nosed pliers. Once you get the c clip removed you can remove the pronged piece and the spring that gives it tension. After that the rod can be pulled up and out of the steering column. Well.... that is if you have enough room to get the horn rod out of the steering column without hitting the roof. If not enough room to get it out you will need to pull the steering column.
If the insulator piece is bad you will need to order a kit for minimal $'s from one of the vendors to repair it.
Please remember to use as little heat as possible when re-soldering the wire at the end as too much heat can melt the insulator piece.
If you don't have someone to help hold the horn rod in place while you remove the clip you can use a c-clamp to hold the rod against the steering wheel while you remove the two pronged piece.