2008 tc Refrigerant Leak "hissing" sound
 

Hello all, i had some A/C issue with "Hissing" coming from under the dash towards the center. The A/C stopped working and after adding 1 can of 134a it all leaked out within a day or 2. I researched and found i had a recall for an A/C hose and gromet which was apperantly done but the dealer didn't try the A/C after the job i guess. Now post recall i tried putting 2 cans in while on a trip and it lasted the entire trip with no hissing sound until we got close to home. By following morning no Cool A/C. I've looked for leaks outside the vehicle, but something tells me the "Hissing" coming from under the dash somewhere is the cause. HOW do you access that area? Does the entire dash need to be dissambled? Am i only hearing some kind of vacuum NOT related to the leak? Any help is appreciated.

thank you