Doom & under dash lights will not turn off

if you google Where is flasher relay located on 1999 Chevrolet Silverado 1500 you will find answers.
Look above the fuse box under the left side of the dash to locate the flasher unit. The flasher is a square unit that looks like a relay. It will have its own receptacle mounted separately from the fuse box.

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What lights ? And won't start how ? The clicking is more then likely a relay or a module of some sort . When you turn the key to the start position does the start engage an spin the motor ? Or nothing happens , a crank no start or no crank no start !

Replace the brake switch. Located at the brake pedal arm, under the dash.

In the 1999 Chevy Silverado 1500, the headlights are not designed to be on all the time by default. They are typically controlled manually by the driver using the headlight switch, although some vehicles may have a daytime running lights (DRL) feature. If the headlights are continuously on, it could be due to a modification or wiring issue, and it's recommended to consult the vehicle's manual and seek professional assistance if needed.

sounds like you need to check some fuses does your radio and air control lights come on @ all or your interior lights when you open the doors you have two places that fuses are located one under the dash and the other in the engine compartment your user manual should show you where to locate them and you might see a diagram to see what fuses are for what components on the car my truck has a pannel on the driver side of the dash it is a triangle shape pannel that pops out so it can be tricky to locate the fuses some times

check the brake light switch at the pedal

if you can trace the wires and look for a loose jack or broken wire

I had this problem while moving. It turned out to be the trip odometer was stuck.

WHAT YOU MIGHT CHECK IS THE FUSE FOR TAILLIGHTS, OR DASH LIGHTS. THEY WORK OFF THE SAME FUSE. IF THE FUSE IS BLOWN THE HEADLIGHTS WORK BUT NO TAIL OR DASH LIGHTS