3. Inside the storage area of the Focus, there's one plastic thumbscrew holding the housing in place. Once that's removed, the housing separates from the car. On Focus sedans (and many other cars) you don't even need a screwdriver, as the taillight housing is held in place with three thumbscrews that are accessible inside the trunk and easily come off using your hand.
4. With the thumbscrew and Phillips head screw removed, the entire housing lifts up away from the car.
5. To access the bulb in the housing, simply turn the bulb socket counterclockwise as far as possible and pull it out of the housing. At this point you can inspect the bulb and see if it's burned out. If the filament is broken, then the bulb needs to be replaced. To remove the bulb from the socket, hold the socket with one hand and pull the bulb out with the other. Some sockets require that you turn the bulb to remove it. This type of setup has notches in the socket, and the bulb is keyed with tabs on the base of the bulb so it fits in the socket only one way. Most newer vehicles, however, are simply a plug-in setup.
6. The standard taillight (or running light) and brake light are contained in the same bulb. Both filaments are visible here for both functions. If one of the two filaments is broken, then the bulb needs to be replaced.
7. At the front of the Focus are the headlights, sidemarker lights and optional driving lights. Replacing the headlights and sidemarker lights is a snap. No tools are required.
8. Access to the headlights is from under the hood. The plastic bulb cover rotates counterclockwise and comes off in your hand.
9. The headlight is a bulb unlike a sealed-beam lamp as used in older cars. With a sealed-beam headlamp, there are usually two or three screws and a ring around the headlamp that hold it in place. Once the light is removed, it unplugs much like the bulb shown in these photos. Getting back to the headlight bulb shown here, it removes and installs much like a standard taillight bulb. The three-pronged setup makes it so the bulb will only install one way. Simple and foolproof. In the Focus, there's a wire clip that holds the bulb in place inside the headlight housing. It swivels out of the way for removal and reinstallation.
10. The filaments in the headlights are similar to those in a standard taillight. There are usually two filaments — one for the lowbeams and one for the highbeams. If your car has separate lights for high and low beams, then there will only be one filament inside the bulb.
11. Access to the sidemarker lights is under the front fender. Simply hold on to the socket and turn it counterclockwise to remove it from the housing. Inspection of the bulb is the same as with the others. Check to see if the filament is broken. If so, then a replacement will be necessary.
Other Types of Vehicle Lighting
Your vehicle owner's manual contains a wealth of information concerning the inspection and replacement of lighting. The list of exterior bulbs to keep an eye on found in the Focus owner's manual is applicable to almost all cars and trucks. It says to check the operation of the following frequently: headlights, taillights, brake lights, high-mounted third brake light, turn signals (front and rear), backup lights and license-plate light. The Focus owner's manual also provides a chart with the trade number for the right bulb for all the above-listed applications, in addition to the interior dome light, map lights and luggage compartment lights. The Focus owner's manual contains information on how to replace various secondary outside and interior lights, as should any good automotive owner's manual. If you don't have a copy of your vehicle owner's manual, you can order a replacement from a local dealership that sells your make of car or truck.