My expense is your knowledge.
Ok, so I tried
this polishing fix with the
Turtle Wax Headlight Lens Restorer kit. It didn't really work. However, during the process I realized the back side of the tube has a texture to it. Thinking that textrue was interfering with the light, I commenced to polishing it down to shiny (just in the portion of the tube that wasn't working) with the 4 step polishing pads in the kit. It made a small difference but the second half of the tube was still dimmer than the first half.
In the middle of this, I broke one of the tubes. So, I started experimenting with the other tube, since I was going to have to buy whole stupid trim piece, now.
I realized (by hooking up the dash and plugging in the good light tube to the dash without snapping it in) that by placing my hand behind the light while it was on I could see that the light was brightest where the texture was.
That's when I realized that the texture on the back of the tube is probably there on purpose, to deflect the light toward the front of the tube. So, I took some super rough (like 80 grit) sand paper and VERY lightly scratched the back of the tube perpendicular to the length of the tube. This actually helped a lot but it takes a lot of fine tuning. You have to start with fewer scratches at the light end of the tube and gradually increase the scratch density toward the non-lit end.
I got bored with it because I'm going to have to buy the whole trim piece now, anyway. So, I didn't take the time to perfect it.
So, if you have a dim tube (I feel like there is a joke in there) and are feeling brave, the following process may (emphasize MAY) work for you.
PROCESS PROVIDED AT OWNER'S OWN RISK. (Don't sue me, bro!)
TIP: You can clearly see the texture and future scratches you'll make by shining a small LED flash light down the non-lit end of the tube. With the light shining down the tube, rotate the tube until the texture/scratches are away from you. The light tube will act as a magnifying glass and you can really see the detail of your work!
Be warned. This is going to be super fiddly. So, if you don't have a lot of patience, maybe just buy a new trim piece.
1. Follow the disassembly process in the video mentioned above.
2. Reconnect the dash trim plugs back to the car without the tubes in it, but don't secure it to the dash. It'll hang there just fine. It doesn't weigh so much that it'll damage the wires.
3. Use the polishing compound and get the tube nice and shiny. Don't go to town on the back of the tube. The front is the important part.
4. Plug in the light tube, without clipping it into the dash panel.
5. Place your hand behind the tube, moving it up and down the length of it to find the dim sections.
6. Mark those places with a sharpie. It's ok, all you have to do to remove the sharpie is color over it with a dry erase pen, and wipe it off.
7. Remove the tube.
WARNING!!! GO SLOW ON THIS NEXT STEP!!! ONLY MAKE A COUPLE SCRATCHES AT A TIME, UNLESS YOU FEEL LIKE POLISHING IT ALL BACK DOWN AGAIN.
8. Between your marks apply a FEW scratches perpendicularly to the tube with some 60 or 80 grit sand paper. REMEMBER THAT YOU MOST LIKELY WANT FEWER SCRATCHES CLOSER TO THE LIGHT SO THAT THE LIGHT DOESN'T GET TOO ATTENUATED ("USED UP") BEFORE IT GETS TO THE END OF THE TUBE.
9. Repeat steps 5 - 9 until you get an even distribution of light.
I don't know if this process will make it as good as new, since I broke mine. Most likely, it'll be as good as the amount of time you're willing to put into being slow with it.
Edit: Here is the difference it made for me, just with the amount of lazy effort I put into it.
Not my car but exactly the same as I was seeing...
Ignore the right side being dark. That's the tube I broke.
Another pic in full darkness.
