Update- Last night I got ready to troubleshoot the system, and the first thing I checked was the fan belt, and it was pretty loose. I tightened it up, thinking this was the culprit, and went on to change the horn that was in it (not the original) to a bell type ooga horn that came with it. I was so sure that the problem was fixed, I worked till dark on the horn, then took the truck for a test drive. The belt tightening didn't solve the problem, so I'm going back out to do what I should have done yesterday, starting with the voltage regulator and then on to the generator if necessary. Anyway, the belt was very loose, although I just put it on a month or so ago.
