I went thru hell with my 01 Tahoe HVAC. Before doing any mechanical
work, try this: Remove the radio fuse and the heater fuse for at least
10 minutes. The fuses are behind the panel in the left end of the
dash. This will cause the unit to re-initialize and find its stop
limits. It's worth a try, and yes the dealer doesn't have a clue about
If Mr. Goodwrench knew how to use his equipment, he could diagnose this
problem, but that ain't gonna happen. I had my Tahoe tied up in
warrenty work for months. I just would not accept the car till it
worked right. I had to force the issue thru the BBB arbitration.
Derek is probably right, but you should try anything before tackling
this nasty job.