DBates: further to my last post. Dug around the MH and found my receipts. This all happened Dec 2013.
When they thought it was the fan clutch, they put a new one on. Took 1.5 hours of labor. The clutch, 8A616, cost $279. As I recall, they did it all from the underside and it wasn't a big deal.
Climbed a hill near the Garage and same thing. That didn't fix it so all that was left was a sensor. I can't remember which one or what it was doing. The garage ordered it from a Ford dealer and I picked it up. Part number is "9L8Z-6G004-C, Sensor Assy, $39.29". The garage installed it for $25. Did not take long. Climbed Black Mountain to Asheville (a pretty good long grade) and all was normal. A year later and several grades later, no problem.
Good luck!
