After testing, it appears that the problem was dripping condensation from the air conditioner. With the water system under pressure, I couldn't produce wet carpet despite all my efforts. After shutting that off and releasing the pressure, I cranked up the air conditioner and let it run several hours. Finally, I started to get some dampness. I shut it down before it got too sloppy.
After letting it dry for another day, I followed the advice mentioned in several other threads and ran a "weed eater" line up the drain hose as far as I could push it and then clamped the lower end in the chuck of an electric drill and spun it for a minute or so. When I started the A/C up and started to get water draining again, the flow was noticeably increased, and I saw a pretty good amount of dirt particles and at least one recognizable insect wing.
I'm keeping my fingers crossed and hope that this has got it fixed.
Mike & Diane
"The written word will soon disappear, and we'll no longer be able to read good prose like we used to could." - James Thurber