Start with the basics by checking fuses & relays.
I’d also recommend picking up the factory service manual or membership to alldatadiy.com to get the wiring diagrams for your year/model ride. With that you can figure out where to start testing. Good luck...
'98 3.8L Convertible (Red w/ White top)
’07 Shelby GT500 (White w/ Blue racing stripes)
YouTube Channel: Pet Rock’s Garage