Chrysler Repair: AC Quits after 2 hours 2007 Chrysler Pacifica, 2007 chrysler pacifica, chrysler pacifica

Question
Hi,
I just returned from the dealership to tell them that after 2 hours my AC on my 2007 Chrysler Pacifica stops working. (Highway driving).  If I shut the car off for 20 minutes and restart it it will work again for 2 hours.  Also, during this time while driving in the mountains of PA, the AC blows smoke like through the vents.  I think that might be a temp change.
Any ideas?  Dealer says he saw it once, had another car apart for a week and couldn't figure it out.
Thanks!

Answer
u have an evap temp sensor bad. Its either inside the evaporator  or on the H block outside.  What happens  is after u drive for awhile the evaporator will freeze up and not allow any air to go through it  until u stop for 20 min  and it will deice and melt away the ice inside there. The sensor stops the evap from freezing up by telling the compressor to cycle and keep it at say 40F. DId u tell them about the smoke coming out of the vents after the 2 hours?