Hello, i am having an issue with my a/c on my 2011 ram 3500. It works fine for about 30 mins to an hour. Then all the air stops blowing. Does not come out any of the vents but you can still hear the blower motor running. Shut off the truck, sit for a few min then start it back up and it works fine agian. It has the dual zone with the automatic setting. Any idea what is going on , oh yeah and it doesnt matter if you switch it to any other venting options it still doesn't blow out any air.