I tried the A/C and only got a hum. Couldn't tell if fan or compressor so on the roof I go. Old 1991 Duo-Therm, original to camper. Shell is brittle and close to needing replacement but not now. Looking inside the A/C I saw the fan blade was hitting the coil housing and so could not turn. The hum was the fan motor trying to run and that is a good thing.
Looking at the fan blade I saw where the plastic had split. The fan shaft had rusted inside the blade to the point it had split the fan blade causing it to expand larger than the opening it was to fit. The fan motor shaft was bad rusted to the point it was half the normal diameter.
Since the blade had to be replaced I went to our local dealer. The blade part number had been changed three times but they had one in stock for less than ten dollars so I bought it.
Back on the roof I used the saws-all to cut motor shaft to remove old rusted part. Took the side grinder to make a new flat on the shaft for the new blade. Mounted the new blade to the refurbished motor shaft. A/C now running like new and cooling. All done for a little labor and ten dollars.
Sorry for not taking pictures since pics were the last thing on my mind at the time. I could see having to replace that 25 year old A/C for lots more money that I ended up spending. In the end and not so bad problem after all.