Jul 7, 2020
2
2
VetteCoins
44
Car
1994 C4 Convertible
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ON
Hi everyone I am new to this forum and corvette so please forgive me for my lack of knowledge.

I just purchased a 94 C4 Covertible LT4 with the LT1 motor. When I first looked at the car I was able to get both lights working properly. Both went up and down and lit up when activated by the switch.

NOW, as soon as I turned to key to on position both headlights come up whether in off, on, or accessory light position. When I start the car up, even when light switch set to off, the lights try to go down, stop about 1/2 way and the return to full open. I cannot get the light to fold back down when the car is running. And they will only fold back down when the switch is set to OFF and the car is turned off.

Note that while set in off and drive through parking lot the lights tried to go down but went right back up.

Could this be something binding in the light forcing it to open again, switch problem, or DRL problem ..glad they both work but wish I could get them down for daytime driving.

Thanks in advance for all your help!

Cheers
 
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The headlight motors have a knob on top of them. Turning this will open or close the lights as a safety feature in case of motor fail.
Trying these will let you watch how the mechanism is working and might show if its hanging up at some point.
There are bushings in the motors that are subject to wearing out. As yours seem to work it might be that the bushing work was done but reassembly of the operating mechanism was not properly done.
Might also be an electrical or switch problem. It seems from your comments the lights try to go down but then roll right back up.
Something has to be providing an of /off switching.
Try a google search, its amazing what you can find .

Good luck.
 
I have read about that problem ,but I understood it was only on the earliest C4's and they dropped it. My 91 has no DRL.
Maybe a simple unplug it and go full manual.
If you put. 4.2 ohm resister across the sensor it will stop the auto light feature. Nothing to do with the DRL. It uses fog lights. My lights would go up and down every time I went past a tree and they were in the shade. Easiest fix was to turn off the twilight sentinel. The resister did this by making the computer always see sunlight. When I want headlights I just turn them on.
This worked on my 93 C4.
 
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I've been trying to fix the same thing and put a 100ohm resistor in parallel with the sensor. Thing is I'm 100% a rookie when it comes to wiring so I'm not sure I did it right because the lights still flip up when I turn it on in the garage. I'm not sure if it is because I haven't soldered the connection (I was testing before going down that road).

I've attached a picture. Any thoughts on what I'm doing wrong?
 

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Hi swatallguy, nothing really wrong with what you have done for testing purposes. According to Baver you need a 4.2 ohm resistor, not a 100 ohm one. once you have it all sorted out and working to your satisfaction, solder it to make sure you have a good connection and heatshrink to keep it from shorting out and doing weird stuff. Good luck and let us know how you make out.
 
Thanks for the tips. I had seen Baver's 4.2 ohm suggestion but had already gotten the 100 ohm resistors based on suggestions I'd seen in other forums. I'm not much in the way of electronics but would the difference matter in this context?

Dannyboy, do you mean the space the sensor is sitting in or actually modifying the sensor?
 
Hi Swatallguy, yes, the resistor will make a major difference. You are fooling the car into thinking there is always light. Basically the resistor has to match the output from the sensor, within GM's tolerances, for it to work.
 
Thanks for the tips. I had seen Baver's 4.2 ohm suggestion but had already gotten the 100 ohm resistors based on suggestions I'd seen in other forums. I'm not much in the way of electronics but would the difference matter in this context?

Dannyboy, do you mean the space the sensor is sitting in or actually modifying the sensor?
The sensor is in a round tblack plastic insert in the dash pad over the speedometer.
Originally the light is let in through a hole approximately 1.5 mm in diameter.
I opened the hole in mine up to around 2.5 mm.
As more light is let in to the sensor, it thinks it is brighter thus no annoying headlights.
 
Just wondering if the 4.2k resistor worked to disable the auto-headlamps? I’ve got a (Canadian) 1990 C4 that I would also like to disable this on as the headlamps are always switching on/off every time I move the car in or out of the garage. Very annoying “feature” for sure.
 
Just wondering if the 4.2k resistor worked to disable the auto-headlamps? I’ve got a (Canadian) 1990 C4 that I would also like to disable this on as the headlamps are always switching on/off every time I move the car in or out of the garage. Very annoying “feature” for sure.

You have two separate problems. Both home repairs if your at all handy. The first is a 4.2 ohm resister needs to be put across the two leads the the sensor. It’s on top of the dash above the speedo. Just pop it up and put the resister across the sensor wires. This will tell the computer it sees sunlight and it won’t turn on the headlights. When you need headlights just turn them on. The second problem is you need to rebuild the headlight gears. Get the kit, it’s readily available. I got mine from Corvette depot. I think it was about $35.00 or so. There is a couple of really good videos on Utube that show you how to do this. I did mine on the kitchen table. Again you can do this your self just take your time. Took me about an hour per side. Both problems are very common and easy for the home mechanic to do with a few tools.
 
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You have two separate problems. Both home repairs if your at all handy. The first is a 4.2 ohm resister needs to be put across the two leads the the sensor. It’s on top of the dash above the speedo. Just pop it up and put the resister across the sensor wires. This will tell the computer it sees sunlight and it won’t turn on the headlights. When you need headlights just turn them on. The second problem is you need to rebuild the headlight gears. Get the kit, it’s readily available. I got mine from Corvette depot. I think it was about $35.00 or so. There is a couple of really good videos on Utube that show you how to do this. I did mine on the kitchen table. Again you can do this your self just take your time. Took me about an hour per side. Both problems are very common and easy for the home mechanic to do with a few tools.
Regarding the gear replacement. It depends what the motors are doing. If they move lights but "run on" for a few seconds after the lights are fully up or down, then its the delrin bushings. I replaced the bushings on mine several years ago and been fine since. The bushings were less than $10.00 from Corvette Central. Good Videos on youtube.
 
My gears and the headlight mechanicals are fine. I just want to get rid of the annoying auto-lights turning on/off every time I go in or out of the garage or even just turn the key on while it’s inside to work on it.
 
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