How do I get cover off my 98 chevy silverado third brake light?

The tail light fuse is under the rear seat on the drivers side.

Have you checked the brake light switch by the brake pedal?

There is a module under the truck, passenger side towards the back. replace this.

I've worked on these the first drove me crazy. its the turn signal switch every thing runs thru these. head lights, turn signal, brakes. except the third brake light. it runs directly from the brake switch. go figuare

If it has a trailer harness ,check this harness,you may need to replace it.

same bulb but 2 seperate elements. wiring diagram u should be able to obtain from your local auto parts store like autozone(preferred)

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

most of the interior lights can be replaced by popping off the cover and pulling the bulb. usually there are just a few plastic clips that hold it on. as for the third brake light, there are 2 i believe t16 or t17 star screws that hold the lens on. once you have that off, the rest is obvious.

sounds like your bulbs or your fuse is blown

It is a common chevy problem for the circuit board that holds to bulb to fail, are your running lights and signals still working back there as well? If not then you need to replace the boards.