Still loving my 2004 TL but am having funky issue with headlamps burning out. First one burned out around 100,000 and assumed that was normal. Then the replacement burned out around 130,000 (2-3 months ago) and replaced it then. Now today that replacement just burned out. No obvious problem with water inside headlight enclosure. Could it be the control unit or the igniter?

 

replace the ballast

 

Try ebaY

2004 acura tl headlight ballast | eBay

 

Get yourself a pair of new bulbs, it's bad to run different bulbs from side to side. I highly recommend the Osram CBI's, you can find them on sale for around $130 for the set and they are incredible.

Swap the bulb from side to side and make sure that it's not the bulb that is bad. It could be a bad connection to the ignitor or ballast. You can swap 1 part at a time from side to side to figure out the culprit.