As of now, the 2005 to 2007 Focus only has one option for aftermarket headlights.
The Halos in my passenger light went out last week.
Since these halos are the CCFL type, I assumed that both of them going out simultaneously had to be the result of a blown transformer.
This is partially because I've had CCFL tubes inside my car before and experienced many transformer changes.
What you will need:
New transformer (http://www.oznium.com/cathode-transformer)
10 mm socket
7 mm socket
Phillips head screwdriver
Flat head screwdriver / Knife
Soldering iron with solder
Electrical tape / Heat shrink tube
Double sided tape
Remove Headlight. Remove cover for high beam bulb (reflector housing).
and locate a black box with a white label.
The box is attached with double sided tape. Place a flathead screwdriver or knife under it and pry it up.
Theres plenty of extra wire, so don't worry about accidentally removing the halo lights.
I cut the power wires to the transformer in order to make working on it easier.
Once out, pry it open with a flathead screwdriver or knife.
This is necessary to disconnect the wires from within the transformer.
The only issue here is that they are glued in. I used pliers to crush the circuit board and cut the unneeded connector.
Your other option is to cut the wires and solder on the new ones.
Once out, the original connectors will plug straight into the new transformer.
Since I cut the wires going into the transformer, I had to solder them to the new connector.
If you decided to cut these wires, don't forget to replace the rubber grommet.
Reconnect your wires.
Apply double sided tape to the new transformer and replace it inside your headlight.
Reinstall your headlight and make sure everything is working.