Been a while since I've last posted here, but happy to say still driving the 2nd of my 3rd gen TLs, now a 2004 w/ 140k+
Got a Service B last week and asked the local mechanic's help in replacing one of my headlight bulbs that's been out for months. I used to service stuff like this all the time, but lately apartment living (and wfh'ing) makes a lamp replacement where I need to access through the wheel well a pain. Fortunately my local mechanic is very reasonable so I don't mind tossing a few his way to save myself the grief.

He thought he got the lights working, and then when I went for the pickup, no bulbs lit! Just side markers, but not even my fogs which had been great. Ultimately it looks like the ballast on the passenger side is the problem. And now ~$200 more to the repair bill, but even stealerships don't have the ballasts readily available.

What's the specific ballast part number I should be searching for?
I've seen a number of threads here with varying info - as in buying used from a junkyard on ebay is a great way to get for cheap (<$100), and others say buying ebay is just asking for problems. I'm happy to do my own homework but if someone here knows part number and can at least point me in the right direction, or a path to definitely not go down, I'd much appreciate - thanks!

 

If your fogs are also inop, you have a separate (or additional) problem. The fogs run straight off battery voltage. Time to check fuses and wiring continuity.

Back to ballasts. From my research:

Year (Mfr. Model #)
Honda Part #

2004 ONLY (W3T10471)
33119-SCC-003
2004/2005 (W3T14371)
33119-S2A-J01
2006-2008 (W3T13072 or W3T16591)
33119-SEP-H01

Aftermarket: X6T02981

I've had good luck sourcing OEM junkyard pulls on eBay. To find these: cut new items out of your search criteria, and review item photos for rust/corrosion. In my experience, the ballasts always die to corrosion and moisture intrusion. If you can find a clean unit, you should be golden.

I won't go near aftermarket as it all appears to be the same mystery meat from China. You will find lots of these, many referencing the part numbers above, but they are not the same unit.

 

Thanks, and will continue the hunt with the details you've listed.
After the erratic bulb lighting, next check was into loose wires or fuses, and after troubleshooting now thinking it's just the ballast.
When I turned the car on tonight, it was just one light on the driver side (wish I noted whether fogs or headlight, as both same color temp!) and then after turning both off and on on the stalk, toggling brights on and off, I'm back to fogs on both sides, and headlight only on the driver side. Still suspect not the ballast, or maybe ballast + something else?

 

I also have a 2004. I recently had to replace both ballasts. One went out and the other followed maybe like a month later. Honestly I bought one I found on Amazon for pretty cheap and it's been working fine and has held up so far. It's been about 4 months.

 

Remember, fogs are on the inside, headlights are on the outside. Don't worry about testing the high beam here, it's just a mechanical shutter.

If the headlights (not the fogs) are intermittent in turning on, that might point to the igniter. But it could still be the ballast. Usually this is diagnosed by swapping in known good components.

 

If the ballast is in question, might as well replace the ignitor as well at the same time.