The A/C system in my 2011 Grand Cherokee Limited is having some issues. Often works fine, but occasionally when driving the car for +30 min with the A/C on air stops coming out of the vents. Blower motor still audibly running, but no air coming out of any vents. Other times, the system will be fine for over an hour. New to fixing **** myself, but can't find any reason it would work sometimes and not others. Thanks guys