9007 vs. 9004: What's the Difference Anyway?


If it looks like a duck and quacks like a duck...

As the old saying would have it, if it looks like a duck and quacks like a duck then it's probably a duck.. Well, not always.

9007 bulbs look fundamentally similar to 9004 bulbs, they are often sent as interchangeable parts in HID kits, so they must be the same. Right? Not Exactly.

9007 vs. 9004: How do they differ?

These bulbs appear to be nearly identical, but in reality there are a few subtle differences that could greatly impact your finished product.

At first glance, the wiring appears to be uniform between the 9007 and 9004 bulbs; however, that is not the case. Therefore, it is necessary to identify these discrepancies to create a successful modification.

While the connectors look the same and the coloring of the wires is uniform, the ground, high beam and low beam wires have varying placement.
                                                       Single Beam 9004/9007 HID Bulbs                                                                 

The second subtle difference between 9004 bulbs and 9007 bulbs is pin configuration. While you may not notice this tell-tale sign initially, it will be made apparent as you're finalizing your project with the install.  The 9007 bulb has the ground pin in the middle, and high/low positive pins on the outside, whereas, the 9004 bulb 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:
Lastly, we should note the wattage differential between both bulbs. While this difference, will not create any variances in installation, etc. it will create a noticeable difference in the overall output of the bulbs. 9004 bulbs have a wattage rating of 45 watts on low beam and a high beam wattage rating of 65 watts when the high beams are on. 9007 bulbs have a wattage rating of 55 watts of low beam power and 65 watts of high beam power. The additional 10 watts allows 9007 bulbs to be slightly brighter when being ran as low beams. 
Mix and Match?!
Now that we have identified the differences, can we mix and match? In short, the answer is yes! There are a few minor adjustments to be made, but nothing your average car guy can't handle. 
When upgrading your headlights, you will only be presented with one bulb option- either 9007 OR 9004. This bulb must then be configured and adjusted to suit your specific needs.

The HID version of the bulb will have the notches cut out to fit either a 9004 or 9007 bulb and you will simply need to swap the pins around to fit your desired style of bulb:
Winner, Winner....Chicken Dinner?
9007 and 9004 bulbs are so closely linked that it is difficult to determine a clear winner.
However, 9007 bulbs slightly edges out the competition due to its availability and slightly brighter output.
Typically, when receiving this type of HID kit from distributors, the 9004/9007 style blue plug on the relay harness will be configured for the more popular 9007 wiring. Thus giving the 9007 bulbs a slight upper hand as it creates a truly plug-and-play scenario- meaning no modifications are necessary in order to create a compatible relationship between the bulb and the remaining components.
Lastly, 9007 bulbs have a slightly larger power output creating bulbs that appear to be brighter and create more visibility for the driver- especially when running these lights as low beams.

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