I purchased a two back of H11 Halogen bulbs. I had one headlight and one fog light burned out. The headlight still doesn't work but the fog lamp works after changing them out. I read that the Halogen doesn't required a ballast to power up. I am trying to figure out why the headlight doesn't work. My question is this: Is it possible that one of the bulbs (in the two pack) was bad? Or does my mazda cx9 have a ballast for the H11 halogen bulb? I think the whole front bumper needs to come off in order for me to remove the headlight, so if there is no ballast, I don't want to go through all that work. Just looking for guidance, thanks. Eddy

 

Halogen bulbs do not require a ballast and are instead wired to accept 12 volts directly.

1. Try putting both new bulbs on the head lamp assembly that you know works. This way you can eliminate the possibility of one bulb being defective.
2. If one bulb does not work, there's your culprit. If they both work...
3. Use a tester if you have one to confirm that there is current being fed to the harness of the light assembly that does not work.
4. Lights are often fused together in the fuse box but check it anyway.

If a tester does not show current, it's possible the harness is defective and/or the wiring leading to it has been severed somewhere.

 

A common cause of light problems is the negative wire that has become poorly connected to the car's body. Find this, be sure it is clean and tight.

 

Check the fuse.