My low beam passenger side bulb blew so I stopped at Advance Auto and replaced it in the parking lot. Later the same night, it blew again. I thought that maybe I got a bad bulb so I went to Auto Zone and replaced it again with the same brand of bulb. This one lasted about an hour before the same thing. Both were Sylvania H7 bulbs. What could possibly cause only one bulb to constantly burn out so quickly, poor quality bulbs or another issue? I have not checked the voltage at the connector yet but I will. Has anyone had problems using aftermarket headlight bulbs?

Art is the winner and I feel like a dunce. After checking more closely and comparing the passenger side to the driver's side low beam bulb, I had installed both failed bulbs turned 90° off. I 'assumed' it was correct since the spring clip latched easily. Thanks for the help.
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2004 XC70

Over voltage will kill filament lamps, get a DC voltmeter and measure your
voltage at the battery, you're looking for about 14.0 VDC with the engine revving.
That would not explain why a single lamp would die, but see what you have since if
it's too high you need to fix it.

Is the lamp flickering? maybe a loose connection? Perhaps a flaky bulb out sensor relay contact or loose crimp at the connector.
Is the bulb out sensor lamp working? see if it comes on when you start out.
Look to see if it's triggering.

Touching a quartz halogen lamp puts skin oil on the glass, the high temp reached
with those lamps will discolor it. If you do touch it, wipe it off with 90%
isopropyl alcohol that you get at any drug store.

Bill

Thanks for the reply. I will check voltage and amperage at the connection tonight and the connections at the bulb. If voltage is over normal, what could cause this at one particular terminal? The sensor is working correctly. It comes on when the bulb burns out.
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2004 XC70

Don't bother with amperage, see if the volts are high since that kills bulbs.
If just one lamp is burning out is weird. Look for a loose connection that might
cause the lamp to flicker ...on off on off... that might croak the filament.

Thanks for the advice. I'll check these items and buy another bulb of a different brand to see if that helps. A loose connection makes more sense than anything else.
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2004 XC70

Are you sure you have seated the bulb correctly and that the spring you flip over and lock the bulb, seats correctly. they also warn you about touching the bulb glass during installation.
Art

Yes, I made sure it was seated correctly and only handled them by the base. That is what puzzles me, they were installed correctly yet burn out in a matter of an hour. Thanks for the suggestions.
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2004 XC70