Brake Light Question

I remember after months of memorizing essential truck driving information prior to trucking school, I came across quite the conundrum and I was wondering if someone could help me answer this. My question has to do with the air brake system and more specifically the stop light switch. Okay so the air compressor sucks in air, stores it in the air storage tanks and when you depress the brake pedal it sends air to each brake chamber to activate the S-cam drum brake (air forces the push rod out, push rod forces the slack adjuster to cause the "S" cam to rotate, S-cam forces brake shoes to push together with the brake pads and finally the brake pads create friction with the brake drum causing the truck to slow down) and at the same time air also triggers your brake lights to come on. But what if you unknowingly drained your air to idk, 0 PSI or whatever isn't enough to trigger the stop light switch? Such as your storage gauge(s) are faulty, meaning it doesn't trigger your low air pressure warning when your psi drops too low. Kinda sounds like you'll brake check the poor b*stard behind you without any warning after your emergency brakes activate due to not having an adequate amount of air pressure to hold back the springs.

Best regards, John

 

Oh I forgot to mention the air compressor, or other essential part experiences a catastrophic failure (falls off the rig and takes out a guy on a scooter for all I care), thus stopping the flow of air to the storage tanks.

 

If that's true then the practice tests I took lied to me lol

 

Hey that was last night and wouldn't that be the problem?