Chevrolet Repair: My Air Conditioner, chevy silverado, feon

Question
I have a '98 Chevy Silverado ext. Cab with the 5.7L V8
When I turn on my A.C. on its highest setting it blows cold for a few seconds, or a minute at most, And then It shuts off. If I wait a little while and try again it will do the same thing but if i Put it on lower settings sometimes it will work. Thanks for the help.

Answer
You may have blocked air box, or simply a low freon charge in the system.  A low charge will cause a cold to hot condition especially on high, due to the fact that you are cooling the evaporator quicker when the fan is on high. if you have a low charge the feon will not sit long enough on high to keep cool on the low side of the system
Have someone do a pressure check to see what the pressures are.
Jimmy