Brake light bulbs used to be fairly quick and easy to change. In more modern times, however, this task has become considerably more difficult. The 2005 Ford Focus offers a few unique challenges to brake light bulb replacement, depending on your car model: Whether you have a sedan, hatchback or wagon, you can have the bulb replaced in about ten minutes.
Open the boot, if you are working on a sedan, and move to step 2; if you are working on a hatchback, move to step 3; if it's wagon, move to step 4.
Directly behind the lamp assembly containing the burnt out bulb is a black trim cover that goes across the back portion of the boot. There are several knobs holding this panel to the Focus' body. Unscrew the knob closest to the lamp assembly and remove it. Once the knob is off, pull the trim cover away so you can reach your hand down between it and the body of the car to access the brake light socket. Now skip to step 5.
Raise the hatchback lid and locate the plastic trim covering the backside of the tail lamp assembly. Slip your fingers under the bottom lip of the trim and pull outward until it pops loose. Once the trim is off, move to step 5.
Raise the hatchback and locate the trim cover on the side of the cargo area directly behind the tail light assembly. Remove the trim knobs that hold the plastic trim in place and then pull off the trim by hand. Once the trim is off, move to step 5.
Grab the brake light socket and turn it counter-clockwise ¼-turn. This releases the socket from the retaining ring that holds it in place. Now, pull the socket upward, so that you can pull the bulb out with your other hand, then push a new bulb into place.
Reinsert the socket and turn it ¼-turn clockwise until it clicks into place in the retaining ring.
Reinstall the trim in reverse order of the removal process and then verify the brake lights are working properly before driving your car.
If your high-mount brake light bulb burns out, you will need to remove the Torx-head screws from both sides with the Torx-head screwdriver. Next, pull the lens off, pull the bulb out, push the new bulb into place and reinstall the lens.