No power to the AC/heater control panel

Hello, hoping someone can help me diagnose why I have no power to ac/heater control panel on my truck listed above Sierra. Just had an arctic storm come through Texas with several days and nights of hard freeze temperatures in the teens. I started my truck and let the motor get up to temperature, before attempting to turn on the defroster and heater. I went to fill up with gas and turned on the defroster as I left my driveway, the fan was blowing and panel was lit and everything seemed to be working, but I did not notice a lot of heat from it but figured it was because of the extreme cold and takes a while to bring the engine temp up and the fluids to get hot enough on older truck like mine. I filled up with gas and returned home and parked in my driveway and it still did not seem to be blowing heat, so I switched the defrost to heater vents and just as I put the fan on high the control panel went dark and blower stopped as if a fuse had blown.I checked the fuses in the fuse box on the lower left side of my dash panel all fuses see to be good. I have been trying to find a diagram or some advice from anyone online that has experience with my model of truck who could walk me through some trouble shooting steps to figure out if there are other inline fuses either under the hood or within the AC/heater system or how to test the control panel itself or if there are any relays or modules to check. I don't feel that it's the blower since it was working, my heater core has been replaced once but all other parts are original, it seems like an electrical issue has occurred. Any help or advice would be appreciated since many modern day mechanics do not know how to work on these older vehicles. I have had this truck since it was new in 1989 so I am very well orientated will how most everything works and quirks with it and most of the time end up doing most repairs myself unless special tools are required that I may not have. There was a lot of ice and snow with this storm which we rarely see in Texas anymore so I am not sure if that could have had anything to do with it. I know at one time I was told by a mechanic that there is some sort exhaust opening in the cowling on the passenger side, I am not sure if that is intake or output or if it has anything to do with it at all, but I did make sure I clean as much ice and snow from the cowling as possible before even turning the defrost/heater on at all. Any help, support or guidance would be greatly appreciated as many mechanics here do not have the knowledge of how to work on older model classic trucks like mine. Thanks and God Bless, I hope to receive a return message soon. GM gave me a part number of
15-73722 for the control panel should that be the problem but they are no longer available as many parts for my model truck so I would have to find online or third party. Attaching a photo of what the control panel looks like.