2003 Chevy Astro cooling cuts in and out

My 1st guess would be the fan clutch isnt working properly and when the engine revs up, instead of the fan clutch speed raising also, it doesnt and the ac high side pressure gets too high. The compressor has a switch that cuts off the compressor under high pressure conditions to save the compressor.

Another possibility is that there isnt enough freon in the system. At idle, the pressure may be just high enough to keep the compressor engaged and cooling, but when the engine rpm's are raised, the low pressure which may be on the borderline of being too low to turn on the compressor, gets so low that the low pressure switch cuts off the compressor. The pressure will rise and fall if too low, thus causing the compressor to kick on and off.

Hope this helps.