AC compressors keeps kicking off

Our company currently has a 2007 International 8600 (Day cab). The ac has stopped blowing cold air. Our maintenance person charged up the system to the following: 140 psi on the high side/ 20 psi on the low side with a total amount of refrigerant at 1.9 pounds. After it was charged, it blew cold air until it was out to make a delivery. The driver called and said it is blowing hot air again. When the truck returned to our facility, that is when the low pressure side dropped and the compressor kicked off. The problem is that when the gauges are hooked up, it shows the low side drops to "0" and the compressor will kick off. The fault code that is being showed is, I may be mistaken, 6-14-13 A. ( I know the "A" represents an active fault) What I am wondering is if one of the pressure switches, or both, could be bad. We thought that maybe it was the cabin filter which was changed but to no avail. When the gauges are attached, and the ac turned on, the gauges do read 140/20 for a bit then, as stated above, drops to 120/0. Any help would be appreciated.