The Hyundai Santa Fe uses an axillary third brake light. The idea behind the third brake light, especially on wider vehicles, is that it will be easier for the driver behind you to see when you're braking. However, this also means that when the brake lights blow, you have one more brake light to worry about. Fortunately, Hyundai made it relatively simple to replace the third brake light on the Santa Fe.
Open the rear compartment door all the way.
Remove the two Philips-head screws holding the rear plastic trim in place for both the left and right bulb. The screws are located on the side panel between the lamp assembly and the inner part of the compartment door.
Slide the side panels to the left (for the left panel) or right (for the right panel) and remove the panel. You should also now have access to the third brake light.
Remove the electrical connector running to the third brake light.
Turn the bulb ballast for the third light counterclockwise and remove the bulb.
Install a new bulb. The bulb number part you'll need for the new bulb is located on the base of the old bulb.