A/C Control Panel Went Blank/Blacked Out

88-92+ Trucks & Suburbans with digital/button operated Heat & A/C Control - Girlfriend's truck, warm weather, unit was on Vent setting. She hit the blue A/C button, the compressor kicked in, then a few seconds later the entire Heater & A/C Control panel display went black (it's the digital-type control with flourescent display panel). Fan shut off at same time. I checked all fuses under dash, none were blown. Removed dash cover & pulled the control module out. Located '93 module with same P/N at a salvage yard for $45, plugged it in, no luck. Still blacked-out, no sign of life. Are there any other fuses, relays, fusible links in the heating & A/C system, other than at the under-dash main fuse box? It's acting like there is no power getting to that control panel/module. Could it be the ignition (key) switch? Any help or ideas will be greatly appreciated! Thanks in advance. -Dan.