Our front and mid AC units were having issues for some time — mostly not getting cold, and sometimes refusing to come on at all. We got a few techs to look at them, without any conclusive results or solutions.

While staying at Thousand Trails Orlando, we got Charles Sutton of CS Mobile RV Repair LLC to take a look, and he determined that the compressors on both were shot, and we needed to replace them. An unpleasantly large expense, but he handled it very professionally.

Here he is lugging the very heavy AC unit up to the roof (and I appreciate the padding on the ladder to protect our paint):

The offending part:

Inside the old AC unit, partially disassembled:

It is nice to have reliably working AC units now.