There is a door that closes when you select MAX AIR. It falls off of its shaft and blocks the air intake path for the cabin air! Open the hood and carefully snap off the passenger side black grate at the base of the windshield. Remove the painted rubber inspection plate under the grate. Start the truck, turn on the A/C and open the glove compartment door. Look thru the inspection opening at the base of the windshield on the passenger side while someone switches from MAX to normal air conditioning. You should be able to see into the passenger cabin when normal air conditioning is selected. When you switch to MAX AIR you will see the door close. If you don't see it close, it fell off of the shaft and is now blocking the intake air path to the passenger compartment. I bought the air door assembly from the dealer parts department, removed the door from the new assembly. I was able to remove the old door and slide in the new door. I worked from the inside of the car behind the glove box, removing the old door and installing the new door thru a small space between the plastic boxes. I am not saying it is easy. It helps to have the new door assembly to look at and see how the door is installed. I would recommend you have a professional install the door. It's a shame that we have to diagnose our own problems. Hope this is helpful. Actually I hope this is not your problem and it turns out to be something that is easier to fix!