Originally Posted by Diseasel300

The center vents in the dash are conditioned air. Not sure where the idea came from that they were fresh air only.

When in cooling mode, the center vents should always be open, even if the fan is ramped all the way down and the monovalve is cycling.

When in "Auto", the fan should ramp to the highest setting if you have the temp wheel turned to "Max" cold. If you're in the white area, you can expect various different behaviors depending on the temperature in the cabin and the exterior temperature.

The "clunk" you hear when the temp is being reached is probably the "diverter". When the temp is being reached in the cabin, the diverter is moved so that more air can flow through the heater core. If you have a vacuum leak or a bad vent pod somewhere, you can expect some bizarre behavior. The default with no vacuum is to go to defrost.

Make sure your aspirator fan motor works and that the tube to the temperature sensor is intact. If either one is kaput you'll have poor temperature regulation in the cabin.