Hi Bill,
It could just be a failing A/C unit. But, you have a Precision Circuits System that manages power consumption. If there's too much power being drawn, I believe the power is first cut to the water heater, and then next to the rear A/C unit. And I think the blower continues to run, but there's no cooling.
If your rear A/C unit is the one that won't run, try shutting off other 120V AC appliances to see if it starts cooling. If that does not help, you may just have a problem with the A/C unit.