Just a note: While I was in the Challenger Automotive shop in Lake Havasu City late on Friday, December 20, 2013, discussing my Onan generator problem, Bill McVicker received another call from another motorhome/Onan owner with exactly the same error condition, e.g., temperature sensor fault. The other owner was told the identical story as I had just received - come in Monday and we'll order the parts. When the parts arrive, then we'll make a firm appointment to bring in the coach for a one-day in-and-out repair.
I remember Bill pointing out that the temperature sensor's and thermostat's longevity depends in large part on how often the engine's coolant is changed. I have no idea when or if at all the thermostat and belt had been changed since the generator was manufactured. My generator's S/N starts with J02.... That's a 2002 manufacture date - over ten years old. So I elected to get 'er all done.
Except for the expense, this has been yet another great learning experience. And $500 to $600 is relatively cheap after hearing about tow-jobs, alternator problems, leveling issues. I just can't wait to change my eight tires... lots of zeros in that bill.