Roof Air.

Thanks for your responses. Being handicapped I called an A/C repair shop and talked to a tech. Short story was to turn off the system, wait a while then reset the 2 zones thermostat temps as close as possible together. 18 hrs. later so far so good. cycles as required and zone 1 still blowing cold air. I don't understand but it seems to be working. Thanks again. Cost $ 0.00. Today's temp s/b 102.

Ted, I had similar trouble last year when I showed up at Lake Havasu City, too early (Sept. 2012) the air wasn't working all that good. A local told me he thought (which he was right that) that there wasn't enough humidity in the air, at that time the humidity was only 8% as the winter season went on my air got better! I hope you have a similar problem that doesn't cost you $$$! Good Luck, Rooster

Wonder if it is as simple as the compressor cycling.

Agree that cleaning the condenser (done from the roof) is a good idea as far as preventive maintenance.

The condenser coil on the roof my need to be cleaned. A dirty condenser will cause high compressor discharge pressure. High discharge pressure will cause the compressor thermal overload to trip and shut down the compressor which will stop the unit from cooling until the overload switch automatically resets.

Good Luck Don