1994 Suburban brake lights

I always believe to start with the simple things first. In your cause the first thing to check is the bulbs. I know it seems unlikely that all the bulbs went bad together but they could of gone bad at different times and it just wasn't noticed. Next check the fuse and make sure it is good. The next thing to check is the brake switch. Make sure there is power going to it. If there is then make sure when the brake pedel is appiled you have power leaving the switch. If you have power to the switch and none leaving it then the switch is either bad or needs to be adjusted. Hope this helps.