The passenger side always pops up, headlight on. On two occasions, though, the driver's side sticks in the down position. Switching the lights on/off/up/down several times seems to get it going so far. Car ('02 Coupe) now has 8100 miles on it, a true, though former, garage queen.

Any thoughts about what might be happening? Does this portend anything bad for the future?

 

check the plastic stops, they get worn and allow the light to go down too far....you can take them off and flip them over, that may help...

this is what they look like https://www.ecklerscorvette.com/corv...SABEgKIhfD_BwE

 

Sounds like a nice C5 BarneyZ.

The same thing happened on my '00 and it was caused by the rubber boot that you remove for 'manual' operation being pushed on too far. Try removing the boot and see if it makes a difference. If not, you probably just need to drive that pristine car more

 

As mentioned by Pewter99 in Post 2, it's probably damaged or missing rubber bump stops. Have you checked them? You might need to replace them (4 per side).

You can try a simple test by manually beginning to open the driver's side headlight before actioning the headlight switch. If it goes up after doing that, most probably is the rubber bump stops.

In addition to that, there is a TSB addressing those symptoms that calls for shimming the driver's side motor.

 

I am having the same problem with the passenger side. it shuts fine but does not open, sometimes. All my stops are there and in good shape. tested the module and it tested fine.
I ordered a rebuilt motor with a 5 year warranty on Ebay. Stay tuned.
It goes in next week.

 

Try the simple test I mentioned above. If the motor works fine closing and is not producing the well known "rat-rat-tat" noise, chances are your motor is OK and it is just the bump stops that limit the closing action what needs to be replaced (even though they might look fine to the naked eye). The ones that limit the opening action are probably fine, but I would replace all 4.

The way the headlights work is not based on predetermined positions. When the headlight doors open or close and they reach the end of their travel, they press against the corresponding rubber bump stops. As a result the current through the headlight motors increases and that is sensed by the Headlight Door Control Module, which in turns cuts power to the motors.

If there are missing or damaged bump stops, the motor might keep working longer than really needed, which could result in over torque. If that happens, the next time the motor is operated it would require more torque to perform the action. That would mean more current than normal and the possible intervention of the Headlight Control Module, shutting again the motor before the door actually moves.

If manually relieving the pressure allows it to work, then you have a good indication that the bump stops are damaged or scored too deep where the limiting contact is made.

I would do the test and check all rubber bump stops (4 per side). If you need replacements you can order them from here.

 

totally, that's exactly what my 99 was doing. I replace bumper stop and all seems well. It's the one you can only see with the headlight up.

 

Checked the bump stops and they're all there and in good shape. I reversed them, and even installed new ones I had bought for a previous C5 and never used. Same results. It's definitely not my stops.

 

any slop in the assembly? loose bolts? does it bounce at all or is it pretty stable

 

Interesting... Just not to leave anything behind in a troubleshooting process, did you do the simple test mentioned above? What was the result?

All these questions should be checked at this point.

 

Assembly perfect. Got second opinion by a Corvette dismantler. Nothing wrong with the light.

 

hmmmm.....I will say this, my C5 headlights were a constant source of frustration when they weren't just right. It seems that when they are working they work perfectly but when you have a little issue its a royal pain to figure it out.
As mentioned earlier the way the motors work there are only a few things that can cause the issue you are having. The big one being the stops. Unless you have a gear going bad inside there isn't much else.

 

Does it work when manually beginning to open the headlight, to relieve the pressure, before actioning the headlight switch?

 

My passenger side intermittently did the same, and my bumper stops were good. I found by turning the manual control **** one half turn, it would then go up. I believe there is wear on the plastic gear at the lowered position that increases the start torque required, but it had not gotten to the grinding stage. Instead of replacing the plastic gear, I removed the lifting arm, and rotated the plastic gear 180 degrees, thus putting a non worn part of the plastic gear at the lowered position. This avoided taking the motor drive assembly apart. It's been five years, and all is good.

 

That was exactly where I wanted to get at when I kept asking if it worked when pressure was relieved.

If it is overtorquing when closing and is not the rubber bump stops, or excessive play in the linkage, the only other alternative remaining is wear in the plastic gear teeth around the closed position, as you found out

 

Update:

New to me rebuilt motor bought on Ebay for $90 went in this morning. Issue is resolved. No more binding and opens every time.
I do think the new motor is a bit noisier closing though. Not sure if they used brass gears in the rebuild. That may be the reason.

 

That's a good idea. Did not think of doing that. I fought with that motor for an hour replacing it. I bet your method would have fixed it too and saved me $90

 

I also found some slop in the motor mount to gear housing I could not remove. I did not take the gear housing apart to verify, but that slop probably allows the worm gear to move away from the plastic gear, decreasing contact area, and maybe moving the worm gear to a higher friction area. The vendor selling the rebuild kits had a note stating he was evaluating if he could design a solution to more securely mount the motor.