Well, for awhile I have moved the tractor back to the ranch house, so at least the same rat won't be back. Do you think an ultrasonic device will work in a shed with three open sides?
A few months ago I had a terrible case of owl excrement all over my tractor, including the instrument panel. Someone remarked at the time that at least it kept the rats and mice away. The owl cleanup was probably more hassle than fixing the wires, but of course rats can do much more damage than I suffered this time. The owl left on its own, anyway, so it's not like I had a choice.
In case anyone ever needs to know, I used NAPA bullet connectors (part #784467), marked 22-14 Ga. They fit perfectly, but I had to trim the plastic insulating housing.