I installed a new headlight bulb on just one side of my car.

But now this happens when I try switching between high and low beam:

driver side is low beam, passenger is high beam
driver side is high beam, passenger is low beam

My only guess is the new bulb has it's wires reversed in comparison to my old bulb. I'm guessing I'd have to buy another bulb just like my new one if that is the case, but I was wondering -- is there is some other way to make them both high beam at the same time/ both low beam at the same time?

The cable that gives the headlight power only fits in one way, so I don't think that's upsidedown. It is the correct type of bulb, but I think it may be a different brightness level (they are the same brand though.)

Per my vehicle's Manual for Nissan Sentra 1999 - I bought a Sylvania 9004 bulb for replacement.

  • Which vehicle is this on? I think what's happened here is you've fit a bulb with a different wattage rating (which would explain why one appears to be brighter than the other). The wattage is usually stamped on the bulb itself. It would be great if you could post up pictures of the new and old bulbs also.
    – Zaid
    Aug 31, 2015 at 18:14
  • I went to find a picture of the bulbs and I think I found the issue. Whoever last replaced my lightbulb put a 9007 into the passenger side, vs my new (correct) 9004. candlepowerinc.com/pdfs/9004_9007.pdf I'm going to buy a new bulb to replace the 9007, since it shouldn't have been in there in the first place. I will post that as the answer once I verify buying a new bulb fixes the issue.
    – Jemmeh
    Aug 31, 2015 at 18:57
  • Oh, and I noticed this because one bulb said HB1, and the other said HB5 on the side. Same wattage. I do kind of wonder though how much of an issue it really is, since that 9007 has been working for quite a long time. Better safe than sorry I guess.
    – Jemmeh
    Aug 31, 2015 at 19:02
  • 9004 shows two different wattages: 65 W & 45 W. Are you sure the headlamps on both sides have the same wattage?
    – Zaid
    Aug 31, 2015 at 19:12
  • OK, just saw your comments. Keep us posted
    – Zaid
    Aug 31, 2015 at 19:13

1 Answer 1


Some headlight 'variants' are the same bulb, with the same or a similar connector, but different wiring.

9004 and 9007

9004 vs 9007

4656 and H4

4656 vs H4

Because you asked, you absolutely can fix it. There are locking tabs on the terminals in the connectors, you can insert a small, flat pick (there are specific tools for doing so), depin the connector, and repin it into the configuration you like.

Terminal Removal Tool

In your situation, however, the more appropriate solution is to use matching headlight pairs. By choosing similar wattage 9004/9007, you now get to choose whether your 'brights' are stalk forward, or stalk rearward.

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