Bruce, Thanks for your helpfulness...
but that separate temperature sensor is only present in older K's—or at least definitely not present in my case!
What passes for logic is this:
a. Bike overheats in slow traffic, especially quickly at stop lights.
b. When you look inside radiator/fan assembly, you notice fan never rotates, no matter how hot engine gets.
c. Disassembly shows fan-motor clearly like buffalo bill—defunct. Plastic stuff melted into brushes, etc. All very ugly and fully permanent-looking in its defunctness.
d. Associated relay also gives very powerful visual indications of similar defunctness.
e. Obtain "new" fan motor and relay. Both work fine separately and together, but not back on the bike.
f. "Feels" like motronic brain also defunct in the area of temperature-sensing-communication. "
"What else could it be???", as we sometimes say here in Texas...
Thanks again for your thought.