A/C Question

I re-charged the system about 8 or 9 weeks ago and the A/C was doing fine for about 6 weeks. The front started to blow a little warmer when used alone but did OK when running together with the rear A/C. This week it wasn't cooling anymore - there must be a leak somewhere so I took it to the dealer. They said that the was pretty much out of Freon, so they re-filled it, put in some dye and searched for a leak: Nothing. The condenser is fine and the compressor shaft seal as well. They used a sniffer and the black light and told me to run the van for a week with the A/C on and take it back to them for another leak check (free of charge) since it might be a very slow leak. They also mentioned that the evaporator core could leak? They would try to check this with a sniffer (due to accessibility) upon return of the van. Is this a possibility?
Here is a link to a previous post: http://www.automotiveforums.com/vbulletin/showthread.php?t=895073

Evaporator core leaks are very possibile.

I re-charged the system about 8 or 9 weeks ago and the A/C was doing fine for about 6 weeks. The front started to blow a little warmer when used alone but did OK when running together with the rear A/C. This week it wasn't cooling anymore - there must be a leak somewhere so I took it to the dealer. They said that the was pretty much out of Freon, so they re-filled it, put in some dye and searched for a leak: Nothing. The condenser is fine and the compressor shaft seal as well. They used a sniffer and the black light and told me to run the van for a week with the A/C on and take it back to them for another leak check (free of charge) since it might be a very slow leak. They also mentioned that the evaporator core could leak? They would try to check this with a sniffer (due to accessibility) upon return of the van. Is this a possibility?
Here is a link to a previous post: http://www.automotiveforums.com/vbulletin/showthread.php?t=895073

ever seen the valve core leak on a tire ? these can leak on a/c systems too and most people don't know to look for this .any of the seals and o rings in the a/c system can leak . also rear a/c has another 15 foot of lines to look at plus the o rings on it.one other place to check is at the hoses that connect to the a/c compressor if the hoses wiggle then the hold down bolt has pulled out of the aluminum threads in the compressor. easy fix with a longer bolt.