Bought new air condition unit Sept. 2012 for central air all electric home that is ten years old. Air cooled wonderful in September and heat worked over the winter.

When turning on A/C this spring the air was not cool. A/C repair man found the A/C switch in electric box flipped. Reset switch and A/C air was then cooling. After a week or so we had to turn heat back on.

Now it is time for the A/C again and it is not cooling. I checked the circuit box and switch is in correct position. What next can you recommend?

You may have 2 breakers to check at the main Panel(Air Handler and Outside Compressor Unit)
Then be sure you have Disconnects at both units On.
If the Heat still works, The 24 volt transformer is good.