OP here. After adding a can with no change I took the rig to a shop. They found a leaking compressor and a bad expansion valve. They replaced the compressor, expansion valve and dryer. They also found contaminants so they flushed the entire system. They just called me to advise that it's done. Anyhow, the service guy advised me:
* that it's blowing at about 53 degrees. This is 10 degrees warmer than what I had before it let me down a few weeks back.
* that they were only able to fill with 3# because the pressure was getting too high. According to my documentation, this is a 5# system.
I don't know what pressures are appropriate. The ambient temp here is about 100 degrees. I'm nervous that this thing will not be fixed right!
jor