Help! twilight sensor off and headllights will not close

[JPB52]

hi everybody the twilight sensor in my 1999 c5 stopped working some months back and now both my headlights remain in the open position. lights work but the headlights remain up even when i turn the lights out and stop the engine. three weeks ago i had to change the headlight motor of the passenger side headlight. i live in italy and in my area there are no specialized mechanics for corvettes. as much as possible i would like to understand and fix problems myself!
thanks for any ideas and help!

 

[Junkman2008]

The problem is your headlight gear (which ironically is what you last touched). Here's how you verify that. make sure that your lights are off. Lower your headlights using the knob that is mounted behind the motor. using the headlight switch, turn on the PARKING LIGHTS ONLY. If the headlights raise, you have a headlight gear issue. The headlights should NOT raise when you only turn on the parking lights. If they do, that's a dead giveaway to a headlight gear issue.

 

[JPB52]

A fuse was blown so i replaced it and now the headlights close and open but, as you say, when i turn on the parking lights the headlights open. This is a gear issue. How can i fix this problem? does the twilight sensor have anything to do with the problem?

 

[Junkman2008]

No, the twilight sentinel has nothing to do with this problem.

One of your headlight gears is bad and that is the ONLY reason this is happening. It is a tell-tell sign with the C5. If you have successfully replaced the headlight gear on one side of the car and there are no problems with the work that you did, then the gear in the other headlight is going bad. The good thing about your model headlight motors is that they are held together with screws so you can pop it open and inspect the gear and I bet you will find either some missing teeth or some teeth ground down in the middle of the gear. To verify that this is the problem, you can rotate that gear 180 degrees, reassemble the motor and the lights will work as designed. If they don't, then the problem resides where you did the initial repair. This is a common C5 issue.

I did a write about this issue here.