How to replace 2004 headlight bulbs: An adventure!
In order to change the headlight bulbs in your 2004 Ford Focus you will need several items:
1. The adult beverage of your choice.
2. A metric socket set.
3. A small screwdriver.
4. A small mirror.
5. A metal file.
6. A small flashlight.
Proceed as follows:
Open the hood. It is best to start with the passenger side bulb. Using a 10 MM socket with a medium extension remove the screw holding the radiator reservoir and set it somewhere where you'll be able to find it again. The reservoir is now being held in by a clip at its rear. With your screwdriver, gently pry the bottom of the plastic portion of this clip rearward while lifting the reservoir. It should easily slide up and over the clip. Move the reservoir to your right, balancing it out of the way on the engine block.
Note: If you find yourself unable to proceed this far without extreme difficulty put your tools away, contact a reputable mechanic and finish your adult beverage. You have no business rummaging under your Focus' hood!
If, however, you have gotten this far with little or no trouble reward yourself with a pull on your adult beverage and let's proceed, but before we do, check the horizontal metal body parts near the headlight for sharp edges. If you find any, file them down. I found them the hard way. My thumb will get better.
Remove the seal from the rear of the headlight assembly. It's the big black rubber thing about 3 inches in diameter. Gently pull it off and put it next to the screw you removed earlier. Shine your flashlight into the rear of the headlight while holding the mirror behind the flashlight so you can see the rear of the bulb and socket assembly. Behind the wires and to the side and top of the socket you will see a wire spring clip with a loop at it's top. The clip itself is pressed against the bulb and held at the top by a plastic protrusion over which it fastens.
You can do the next evolution by feel. Remembering where the wire loop was, place your finger on it and slightly under it, then lift and push it to the side and over the tab. Holding this sidwise tension, gently pull the wire clip toward the rear of the headlight housing and pivot it down. Grasp the socket with your thumb and forefinger, pull gently backward and it's out.
Holding the socket in one hand, grab the metal ring at the base of the bulb with your other hand and remove the bulb from the socket. Now, holding the new bulb by the metal ring, keeping your fingers off the glass, push the new bulb firmly and completely into the socket. Be sure the wire clip is clear of the bulb wires and that they are inside of its vertical portion.
Insert the bulb and socket assembly into the headlight. Note that there is a small protrusion in the metal bulb ring with two holes in it. They go down at the six-o-clock position. Be sure the bulb and socket are completely set home into the headlight assembly. Wiggle it a bit to be sure it is seated. The two holes in the ring should be visible from the front of the headlight.
Now comes the fun part! (I did this by feel.) With your forefinger pushed the wire clip back up and into the socket. The vertical portion should fit snugly against the back of the metal bulb ring and the upper horizontal portion with the loop should fit over and lock against the plastic protrusion. You can check this with your mirror and flashlight. Also, gently attempt to rock the socket with two fingers. If it's solid you're good.
Replace the rubber seal making sure it is seated completely on to the rear of the headlight assembly. Move the reservoir back into place snapping it over the clip first by pushing down, then replacing and tightening the screw you removed earlier.
Turn your headlights on and test the new bulb. If it works, reward yourself with a pull on your adult beverage. You're gonna need it!
The procedure for the driver's side headlight is the same as the one you just completed. However, in their infinite wisdom, Ford engineering chose to place a rather substantial component fastened to a metal bracket behind this particular item. Yes, there is enough room to get your paw in there, but it ain't as easy as the other side. Now if you feel up to removing this particular piece to obtain more room be my guest. I didn't and was still able to complete the task but not without impugning the ancestry and marital status of the parents of the particular engineer responsible for the layout of these components.
In any case if this bulb works too you're done. Pour yourself another one, you deserve it!
TIP: If you have large hands perhaps you can bribe your wife, girlfriend, or a dexterous 12 year old into helping you with the above. It's worth a shot!