It’s important to know the differences between these 2 headlight bulbs because they are very similar. The wiring also looks the same, but it’s not, therefore you need to be able to identify and modify each one to achieve your goals:
It is truly incredible how many different headlight bulbs exist in the automotive 12v lighting world, why are there so many different styles to choose from? Is one style truly better than the other? Does an H4 headlight bulb produce a better light output than a 9007? Is a 5202 a better fog light bulb than a 9145? These questions come up all the time, and the answers to them are debatable but because of the insane selection of light bulbs available today’s selection of aftermarket LED and HID bulb options can be difficult to navigate.
In order to reduce the amount of products retailers need to carry on their shelves, aftermarket manufacturers have created “one size fits all” types of bulb replacement products. For example: The 9145, H10 and 9005 halogen/incandescent light bulbs all use the same style of base but each one is rated at different wattage levels and produce different amounts of light. In the LED and HID world, all of those bulbs are now replaced by a single bulb, most commonly called the 9005.
Similarly, the 9004 and 9007 halogen/incandescent light bulbs are nearly identical, but they have some stark differences. First is the pin configuration: The 9007 has the ground pin in the middle, and high/low positive pins on the outside. The 9004 has the ground pin on one side, and in the middle and other side are the positive pins for high beam and low beam. In this diagram you can see the differences between these two light bulbs:
When you try to upgrade your headlights that take either a 9004 OR a 9007 with HID you will be presented with only one bulb option, that upon installation, must be configured to suit your needs: The HID version of the bulb will have the notches cut out to fit either a 9004 or 9007 bulb and you will be able to swap the pins around to fit either style of bulb:
If you are looking for a good HID product to upgrade your 9004 or 9007 dual beam headlights to HID, we recommend the new metal-based bulb kit from GTR Lighting. It comes with a pair of stylish and high-tech “swing” bulbs along with a new waterproof relay harness. Normally when you receive this type of HID kit in the mail the 9004/9007 style blue plug on the relay harness will be configured for the more popular 9007 wiring. In order to make this kit work with a 9004 style headlight, all that is required is to swap the pins around to be in the correct orientation.