Air conditioning fades

I would like to ask for some help. I have a '93 Civic. The airconditioner is becoming a problem. What happens is that it works when I start driving but quickly fades. In about 5 minutes to 10 minutes, no cold air.

The dealer was supposed to check it but said it ran fine there. But this is a constant problem. Dealer said Freon looked good but there might be a bad switch.

I hate have a dealer repair shop to the replace everything game so I would like some ideas.

Thanks