The following article, submitted by a professional installer, contains some extremely useful information pertaining to the installation process of our automotive LED lights. This information should be utilized in conjunction with the official LED automotive lighting wiring diagrams.
You do not want to drill through any glass, while installing a custom LED lighting product. Most headlights are made up of two plastic pieces; one clear in the front that will transition to a black or grey colored plastic near the back. I recommend drilling in through the top of the headlight housing if possible. In a few cars it is not. There are three main things to look for to determine the best location for installing automotive LED lights into the headlights.
The LED will hang into the headlight housing by the wires, but only to an extent. You want to minimize the wiring between the automotive LED lights and the hole you drill as much as possible. After you install the rubber grommet, just gently pull up on the wires until the back of the automotive LEDs touch the bottom side of the rubber grommet, or as far as it can go.
In some headlights, you need to drill closer to the front of the headlight because there is no other place to drill. I have only seen this on the PT Curser. The back of the headlight might be blocked off by some metal or some other part of the car. If you drill close to the front, make sure you don't drill in a location that will be visible after the hood is closed. When closed, the hood should cover the hole.
The size of the fuse does not matter because any fuse will protect against a direct short to ground. Look in the owners manual to find a suitable fuse. You want to use a non-critical fuse, so don't tap into the fuse associated with power steering or the main computer. Some good ones include the accessory fuse, radio, or power outlet. I would stay away from power windows and locks because that could be critical in an emergency.
Be sure to insert the wire into the fuse terminal without power. Then when the fuse is reinstalled, it will act as a jumper to supply power to the wire you have inserted. If you get this backwards, the wire could heat up and burn off the outer insulation, in the occurrence of a short circuit. A short can occur when someone closes the hood onto the power wire breaking through the insulation. If you get this step correct, the fuse will simply blow and the automotive LED lights will go out. Then you would simply replace the fuse.
You do not need your own external fuse unless the car is older and does not have a fuse block located under the hood. If by chance the car does have a fuse block, but does not contain a non-critical fuse, then you would also need your own external fuse. No matter which method you use, the wiring is protected in the case of a short circuit, such as burned insulation or a hood closing on the wires.
Just to clarify, you do not need to add an extra fuse into the fuse block located under the hood. You need to locate a non-critical fuse such as the accessory power outlet fuse, or radio-clock fuse. You will pull that fuse out, insert the wire as described in the instructions, and put the fuse back in. If you cannot find a non-critical fuse, you might need to get your own external fuse.
The automotive LED lights will stay on continuously. The only reason you would need a switch is if law enforcement in your local area are annoyed by seeing blue headlights while the car is parked. The good thing is that the headlight accents are not visible while you drive, unless it is during the night and you forget to turn on your headlights!
Total current draw is 0.02 amps. Just to give you an idea, the interior dome light in the car draws about 1.00 amp and the headlights draw about 10.00 amps. This means the automotive LED lights draw about 50 times less than the interior dome light and about 500 times less current than the headlights. This should not drain your battery unless you let the car sit for an extended period without driving it. If you go on vacation for more than a week, you might want to consider removing the power wire just to be on the safe side. My friend wrecked his car but the headlight accents were not damaged. I remember that his car sat in his driveway for about 3 months because he could not drive it. The headlight accents were still on after all that time.
Some people that have had unrelated battery problems like to blame the headlight accents because it is the first thing that comes to mind. The truth is that if you have a dead battery, your battery is either old, damaged to begin with, or you left your radio or headlights on too long without running the engine to charge it back up.
The switch is just for people who prefer more control, but it is not required. I don't recommend one unless you fell like spending the time and effort. You could mount it under the hood or even inside the car and run the wire through the firewall or the rubber boot in the door. I say it is more trouble than its worth. If you must have one, you can use any switch (push button, toggle, slide, etc). Just make sure it is not a "momentary switch" or you will have to hold the switch in the on position all day to keep the automotive LEDs on.