Air Conditioner problems of the 1999 Chevrolet Blazer

The air conditioner has failed repeatedly since about 35,000 miles; simon motors, an authorized Chevrolet dealership and service center, has repaired it four times. They report there is a leak somewhere in the system and that it is leaking freeon (sp?) "but they cannot find it. " most recently, they replaced the compressor, but the problem persists. After running cool for a time, the air conditioner begins blowing hot air. This is usually accompanied by a concentration of moisture in the air inside the vehicle, often with a foul odor. Are we in danger of any toxic exposure from this leak? what other reports of chevy air conditioners do you have on file? it gets extremely hot here in the desert and this problem needs to get fixed, but it is not being fixed. Please advise.

The air conditioning compressor was replaced by the dealer on Friday June 25. After the repair the vehicle was driven approximately 20 miles that day. On the following day the vehicle was driven an additional 25 miles and returned home. After leaving the vehicle parked in my driveway, I was summoned from my home by a neighbor who reported that the vehicle was on fire. We extinguished the fire in the engine compartment and had the dealer remove the vehicle for repair. The dealer informed me that the fire was not caused by their repair. Damage to the under hood equipment required $ 4,500 in repairs. The repair work took over four weeks.