I am also tracking down a cruise control issue on my coach. The current theory is that the problem is in the brake system, as you'll recall that a brake tap disengages the cruise. We're looking first at a problem with the switch connected to the brake pedal because that is so much easier to access than the wiring in the steering column. I note that you said that your horn also doesn't work, and I'll confess that I haven't tried the horn, but I fear that since the horn has nothing to do with the cruise system your problem is not connected with brakes. If you do not otherwise have a fuse block diagram, you can probably get one online.
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