2001 Toyota Corolla AC intermittant

Aloha!

My Toyota blows cold air for about 20 minutes, then the air gets warm. I had an AC guy check it while he was fixing my wife's AC. The AC guy said the fluid is full, and the AC is running correctly and that he suspects an electrical problem. I check the 7.5A fuse that says AC on the schematic an dit is fine. There are also 3 relays under the hood, not sure how to check those. Any feedback would be appreciated.

Hawaiicarl