I have a 1999 Chev Blazer, 4.3 v6, and none of the lights on the control panel for the heat and a/c do not come on therefore, the heat or a/c do not work. Also, rear defrost not operational. NOTHING works on that panel. Any help would be very much appreciated.

Check your fuses. Check the fuses that are by the drivers side door on the inside. Also check the fuses under the hood. Good luck