My vette is a 1999, the headlights work intermittently. Usually first thing in the morning they work fine but when i get to work turn off the car then start it back up the headlights will not work properly, some times the drivers will come up some times neither. I have replaced the gears, headlight module, and verified the operation with twilight on and off, still the intermittent operation. All the lights do come on, just the headlights do not always come up. Any thoughts? Grounds maybe? Any help appreciated.

 

Not at home with my FSM now. If no one else chimes in I can get back to you this weekend. I have researched this design area a little in the past but not in too much detail (yet). Not sure if what you have would throw a code or not but pull them anyway and post. You may have a relay that is going bad. I doubt you have 2 motors going bad, but you never know without some more diagnostics.

 

I had similar issue with my vette,, motor and gears were fine, grounds were good, I found once I removed motor, there is like a plastic bushing that acts as a dead stop to the movement of the headlight going up/down and sometimes in my case, would make the headlight stay up and would be intermediate , these bushing slide offand these bushings are apparently notorious to wearing out and causing a bunch of headaches! Not sure if this will help but I would definitely check it out.

Steve

 

I did some searching in the FSM schematics this morning. There are no codes shown for this issue. There is one relay (44) but it serves both doors and the actual headlights so I have ruled that out. I tried to rule out the Multifunction switch since the actual lights come on. It powers the doors when you manually turn the lights on. However, you said you tried the Twilight Sentinel (with similar issues) and that circuit bypasses the multifunction switch to power the doors. I don't think it is a ground since one side works some times and they both use the same ground. Still could be a ground wire but I don't think so unless it is something in the wiring, not the actual ground connection. Actually could be bad power wire/connection also. You replaced the control module which could have been a likely problem. I think you need to look at a mechanical interference issue like with the bushings Steve mentioned above. If all that looks good we will need to do more diagnostics.

If it works good in the morning and not in the day, it seems like a resistance increase issue due to temperature. Could be actual motors but something tells me two going out at the same time is not real likely but could happen.

Here are 2 pages of door diagnostics from my FSM if you need to go that route. Nothing really special, just straight forward checks. If you decide to use this you will need the pin out info for the connectors which I can provide. You are only going to be able to run the diagnostic when you actually are having the problem.