Chevrolet Repair: Heater and A/C not working, chevy silverado, fan control

Question
On my way home from work this morning I went out to warm up my 2001 Chevy Silverado 1500HD, since it was cold. I noticed that the Air was only blowing out of the Defrost vents on the dash, and that the control panel had no lights working on it. The only control that would make a difference was the fan speed. Have checked all fuses none seem bad. Relays for System appear to be functioning. Maybe I missed something. Any Idea on where to look? Supposed to be below freezing tonight, and long drive to work with no A/C or Heater. Please Help. Unable to contact Dealer at this time due to weekend.  Again the fan control works, just no temp adjust or way to ghange where it goes. only goes to defrost area. No lights working on buttons.

Answer
Hello Robert,
I think I would smack the side of the dash, there to the right of the instrument cluster, and see if a loose connection might be temporarily fixed.
I have had the control module, right there behind the display screen have a bad connection, and unplugging and reconnecting it fix it for a while.

Van