Anyone had this problem? While driving at highway speeds, the air coming from the A/C vents faded away to nothing. It was set on AUTO, temp at 72, recirc not on, set to blow from dash registers. Monkeyed around with selector switch, got better only for a short time, then no air out registers. Turning fan on HIGH, you could hear lots of air under the dash, but nothing out registers. Turned truck off for an hour - restarted - it fixed itself, but only for a short while again. Traveled, then turned truck off for another couple of hours, got better again! Cold air was not an issue - just nothing coming from the vents. Rear air was fine. Never had this problem before. Any ideas?