I removed the "jumped" wire last night and reconnected the wires in what appears to be the factory original way. I was wrong about the jumped wire going into the master cylinder; I just didn't lean down far enough to see that that whole harness was actually going into the cruise servo control. Anyway, everything is back to the way it should have been from the factory. I looked inside the deactivation harness and it doesn't appear to have brake fluid leak. The deactivation switch appears to be functioning properly. The green wire coming to the switch has constant power, and the red/green wire coming out of the switch is hot except when you press the brake pedal, at which time it goes cold. This seems to be functioning properly.
The horn quit working again yesterday. So now I am stumped again. I checked the clockspring again and it is fine. The ground wire coming into the clockspring from below is properly grounded. When I manually ground the big steering plate (part of the horn apparatus in the steering wheel), then the horn button works. I wonder if I have a problem somewhere in just the upper steering wheel...
I would just take it to the dealer, but none of them will work on it since it is a motorhome. I really don't have any faith that an RV mechanic is going to know how to fix this either.... | 
