You can't. The C5 third brake light is an LED unit. If the unit has went out the entire unit needs to be replaced. There are two bolts that hold the unit in that are accessed by removing the rear plate holder.
remove tail light and reach through
Begin by removing the wiring harness from your third brake light. Remove the third brake light retaining screws. Reverse the process to install your new third brake light.
remove the license plate and reach up through that opening. Corvettes weren't designed to be easy to work on.
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Sounds like it may have been replaced at one point with an inferior piece.
From inside the trunk.
the third brake light is direct from brake light switch no fuse
carefully
I assume you only need to change the bulbs. Go into the trunk and look up. You should see the wires leading to the mounting point for the third brake light, you candisconnect the connectors and then change the bulbs this way.
I just replaced a blown third brake light bulb today. ... I have about 60k on my M and havent yet had to change the brake light---so if it only has to be done once in the ... If memory serves, the Concorde's is in the rear window. ... Well I decided to mod my 2004 300Mspecial Third Brake lights, not with a bulb ...
it would be the brake light switch about 20 dollars at autozone