Here is portion of an email from a friend with the same problem.
. Steve, the mechanic, asked many questions about the symptoms and history. He would start by checking the fan performance. It was unlikely, but possible, that the water pump shaft had failed. If necessary, we would be able to stay in our coach overnight with 15-amp power available.
Steve soon determined that the fan was not operating properly. The fan control module was not working as it should. This part has been replaced 4 times since we bought the coach in 2001. I had always been told that it was not a serviceable part. Steve took off a cap and tried to activate the valve manually. It was stuck! He disassembled the other end and eventually was able to remove the piston that moved inside the cylinder. He cleaned and polished the piston, reassembled the system and we retested. The fan was now operating at both high and low speeds. Steve collected a sample of the hydraulic oil for analysis. Steve’s opinion is that a small spec of rust or dust collected in the valve. He recommended that the engine not be allowed to sit for long periods without being exercised….
I drove the coach back to the campground and a few miles beyond with the A/C on to load it up a bit. Ran cool as a cucumber! The Appalachians will be our next real test in another month or so.
