There's another leak if the refrigerant is gone. In most states it's required that mechanics perform a leak check after every AC system service, and if a leak is found, they have to remove / recover the refrigerant and send you on your way or fix the leak and recharge the system again. At the very least, they should be doing the leak check. It's always possible the new hose has a leak, but it's more likely that one of the connections didn't get sealed properly when the part was installed, and even more likely something else is leaking.
To lose the charge as fast as you've indicated, the leak is going to be real big and real easy to find. The previous owner knew there was a fast leak. If all that was needed for a permanent fix was to recharge the system, as he indicated, he would have done that before selling the vehicle.
At this point there's two ways to find the leak(s). All shops that do AC work have electronic leak detectors. They work by detecting the absence of oxygen in the air near the leak. You can also have the mechanic inject a small bottle of dye the next time he recharges the system. Later you search with a black light. The dye will show up as a bright yellow or green stain that will indicate the source of the leak.
Tuesday, July 22nd, 2014 AT 2:25 PM