Gummiente

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C5 owners are very familiar with the annoying “Twilight Sentinel” feature that automatically pops the headlights up in low light situations, such as driving through a tunnel or entering/leaving your garage. '98-up models have the luxury of disabling this feature through the DIC or by pulling a fuse or relay, but this is not possible for the '97 model year. For this year, on Canadian models only, the DIC function was disabled at the BCM by the factory for reasons known only to Transport Canada and the patron saint of Corvettes. However, I've done a fair bit of research on this issue and have come up with three options to bypass this issue, as follows;

1 - By far the easiest and cheapest option is to lift the emergency brake lever up one click before starting the car. If you've ever been to a drive-in theatre within the last 15yrs or so you'll know that this disables the DRL's so that the ignition can be turned on to allow the movie soundtrack to be played through the car stereo. On the '97 C5 this will also disable the Twilight Sentinel and the headlights will stay in the down position. The downsides to this method are that it must be done every time you start the car and the park brake must be lowered once you're in the daylight or you'll have a warning light on the dash and the possibility of a ticket for motoring about without your DRL's lit up.

2 – If you can find a GM dealer willing to work on “old” cars, you can get them to unlock the DIC by using a Tech II diagnostic tool to cancel the BCM input. Then you just switch off the system via the DIC. The downsides, apart from finding a GM dealer willing to do the work, is that you will likely need to pay for this and even then only if you can convince them that this is not considered to be “disabling a safety feature”.

3 – You can remove the defroster vent on the dash, unplug the light sensor and stuff a 4.7K OHM .25W resistor in it's place to trick the system into thinking there is sufficient light not to activate the headlights. It's a bit tricky to do because of the limited working space and you need to be very careful not to drop the connector down into the dash while you're mucking about in there, because a full dash disassemble is the only way to get it back.

Hopefully this info will help other new C5 owners like me and they won't have to spend hours wading through the interweb like I did to come up with the fix.
 

Gummiente

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Sep 6, 2020
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If you decide to do the Twilight Sentinel bypass, here's the procedure I used on mine. Took me about 20min with my arthtitic old hands...

MATERIALS NEEDED
- 4.7K OHM .25 W thru hole resistor
- two lengths of string or long bootlaces
- body panel tool or credit card
- small gauge black zip ties
- electrical tape
- flat tip jeweller's screwdriver

PROCEDURE
1) Using the body panel tool or credit card, gently pry up the closest side of the defroster vent grille, then gently remove it from the dash.

2) Immediately secure the sensors at each end by tying a string/shoelace around the wires just under the connectors and tie off the other ends to the steering wheel and passenger grab rail. If either sensor accidentally pops out and drops down the vent hole, the only way to get it back is a full dash disassemble!

3) Do not remove the large black bulb shaped sensor on the right side of the grille, that is the Sun Load sensor for the HVAC system. The Twilight Sentinel sensor is the small one on the left side of the grille that looks like an LED. Gently turn the sensor 1/4 turn counter clockwise and remove from the grille.

4) Using the flat tip jeweller's screwdriver, gently lift up the side of the connector and then separate it from the sensor.

5) Replace the sensor in its hole and turn it 1/4 turn clockwise to secure.

6) Bend each end of the resistor 90 degrees as close to the resistor body as you can, then insert each end into the pins of the connector, allowing the friction fit to temporarily hold it in place.

7) Cut a 3" piece of electrical tape, secure one end to one side of the connector, then bring it up and over the resistor, securing the other end to the other side of the connector. Then wrap a 2" piece around the connector body to secure everything in place.

8) Turn the ignition to "ON" and verify the headlights do not pop up. Check the manual operation with the headlight switch. Obviously, this step should be done inside your garage/carport.

9) Using a small black zip tie, secure the connector to the underside of the grille as close as possible to the sensor. Remove the strings from the connectors. Ensure the Sun Load sensor is still secured in its hole.

10) Gently replace the grille in the dash and you're done!

MISC INFO
The resistors can be purchased at any electronics supply store or, as I did, off Amazon. They are normally sold in bundles; I paid $7 for a pkg of 25, which was the smallest bundle I could find. Note that the working space is very tight because of the steep angle of the windshield and short free length of the wiring. Don't forget to wipe the smudges off the windshield when you're done. Be very gentle when working with the vent grille, the 24yr old plastic is weak and brittle from years of UV rays.
 
Last edited:

2KforeverC5

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If you decide to do the Twilight Sentinel bypass, here's the procedure I used on mine. Took me about 20min with my arthtitic old hands...

MATERIALS NEEDED
- 4.7K OHM .25 W thru hole resistor
- two lengths of string or long bootlaces
- body panel tool or credit card
- small gauge black zip ties
- electrical tape
- flat tip jeweller's screwdriver

PROCEDURE
1) Using the body panel tool or credit card, gently pry up the closest side of the defroster vent grille, then gently remove it from the dash.

2) Immediately secure the sensors at each end by tying a string/shoelace around the wires just under the connectors and tie off the other ends to the steering wheel and passenger grab rail. If either sensor accidentally pops out and drops down the vent hole, the only way to get it back is a full dash disassemble!

3) Do not remove the large black bulb shaped sensor on the right side of the grille, that is the Sun Load sensor for the HVAC system. The Twilight Sentinel sensor is the small one on the left side of the grille that looks like an LED. Gently turn the sensor 1/4 turn counter clockwise and remove from the grille.

4) Using the flat tip jeweller's screwdriver, gently lift up the side of the connector and then separate it from the sensor.

5) Replace the sensor in its hole and turn it 1/4 turn clockwise to secure.

6) Bend each end of the resistor 90 degrees as close to the resistor body as you can, then insert each end into the pins of the connector, allowing the friction fit to temporarily hold it in place.

7) Cut a 3" piece of electrical tape, secure one end to one side of the connector, then bring it up and over the resistor, securing the other end to the other side of the connector. Then wrap a 2" piece around the connector body to secure everything in place.

8) Turn the ignition to "ON" and verify the headlights do not pop up. Check the manual operation with the headlight switch. Obviously, this step should be done inside your garage/carport.

9) Using a small black zip tie, secure the connector to the underside of the grille as close as possible to the sensor. Remove the strings from the connectors. Ensure the Sun Load sensor is still secured in its hole.

10) Gently replace the grille in the dash and you're done!

MISC INFO
The resistors can be purchased at any electronics supply store or, as I did, off Amazon. They are normally sold in bundles; I paid $7 for a pkg of 25, which was the smallest bundle I could find. Note that the working space is very tight because of the steep angle of the windshield and short free length of the wiring. Don't forget to wipe the smudges off the windshield when you're done. Be very gentle when working with the vent grille, the 24yr old plastic is weak and brittle from years of UV rays.
I’ll stay with my trick of just remove the left and right pop up fuse. Don’t forget to put the fuse pullers back and the fuse in a safe place 🥂😷
 

2KforeverC5

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C5 owners are very familiar with the annoying “Twilight Sentinel” feature that automatically pops the headlights up in low light situations, such as driving through a tunnel or entering/leaving your garage. '98-up models have the luxury of disabling this feature through the DIC or by pulling a fuse or relay, but this is not possible for the '97 model year. For this year, on Canadian models only, the DIC function was disabled at the BCM by the factory for reasons known only to Transport Canada and the patron saint of Corvettes. However, I've done a fair bit of research on this issue and have come up with three options to bypass this issue, as follows;

1 - By far the easiest and cheapest option is to lift the emergency brake lever up one click before starting the car. If you've ever been to a drive-in theatre within the last 15yrs or so you'll know that this disables the DRL's so that the ignition can be turned on to allow the movie soundtrack to be played through the car stereo. On the '97 C5 this will also disable the Twilight Sentinel and the headlights will stay in the down position. The downsides to this method are that it must be done every time you start the car and the park brake must be lowered once you're in the daylight or you'll have a warning light on the dash and the possibility of a ticket for motoring about without your DRL's lit up.

2 – If you can find a GM dealer willing to work on “old” cars, you can get them to unlock the DIC by using a Tech II diagnostic tool to cancel the BCM input. Then you just switch off the system via the DIC. The downsides, apart from finding a GM dealer willing to do the work, is that you will likely need to pay for this and even then only if you can convince them that this is not considered to be “disabling a safety feature”.

3 – You can remove the defroster vent on the dash, unplug the light sensor and stuff a 4.7K OHM .25W resistor in it's place to trick the system into thinking there is sufficient light not to activate the headlights. It's a bit tricky to do because of the limited working space and you need to be very careful not to drop the connector down into the dash while you're mucking about in there, because a full dash disassemble is the only way to get it back.

Hopefully this info will help other new C5 owners like me and they won't have to spend hours wading through the interweb like I did to come up with the fix.
For C5 go to options and turn off Twilight Sentinel. 🥂😷 Cheers !!!
 

2KforeverC5

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Read my first post again. This is not an option for 1997 models. Only 1998 and up can disable through the DIC.
Sorry. Then just go to my old post. If you have the pop up headline. By just removing the fuse for the left and right and forget messing around with electrical. Just a thought!!! 😳🥂😷
 

Gummiente

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Well, that's also an option as well, although I wouldn't be keen on driving around without headlights when it starts to get dark out. And it's a bit awkward to get the fuses back in on the side of the road.
 

2KforeverC5

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C5 owners are very familiar with the annoying “Twilight Sentinel” feature that automatically pops the headlights up in low light situations, such as driving through a tunnel or entering/leaving your garage. '98-up models have the luxury of disabling this feature through the DIC or by pulling a fuse or relay, but this is not possible for the '97 model year. For this year, on Canadian models only, the DIC function was disabled at the BCM by the factory for reasons known only to Transport Canada and the patron saint of Corvettes. However, I've done a fair bit of research on this issue and have come up with three options to bypass this issue, as follows;

1 - By far the easiest and cheapest option is to lift the emergency brake lever up one click before starting the car. If you've ever been to a drive-in theatre within the last 15yrs or so you'll know that this disables the DRL's so that the ignition can be turned on to allow the movie soundtrack to be played through the car stereo. On the '97 C5 this will also disable the Twilight Sentinel and the headlights will stay in the down position. The downsides to this method are that it must be done every time you start the car and the park brake must be lowered once you're in the daylight or you'll have a warning light on the dash and the possibility of a ticket for motoring about without your DRL's lit up.

2 – If you can find a GM dealer willing to work on “old” cars, you can get them to unlock the DIC by using a Tech II diagnostic tool to cancel the BCM input. Then you just switch off the system via the DIC. The downsides, apart from finding a GM dealer willing to do the work, is that you will likely need to pay for this and even then only if you can convince them that this is not considered to be “disabling a safety feature”.

3 – You can remove the defroster vent on the dash, unplug the light sensor and stuff a 4.7K OHM .25W resistor in it's place to trick the system into thinking there is sufficient light not to activate the headlights. It's a bit tricky to do because of the limited working space and you need to be very careful not to drop the connector down into the dash while you're mucking about in there, because a full dash disassemble is the only way to get it back.

Hopefully this info will help other new C5 owners like me and they won't have to spend hours wading through the interweb like I did to come up with the fix.
Am I to understand that you don’t have a separate fuse for your POP UPs? 😳😤
 

2KforeverC5

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As I already said, I do not want to completely disable the headlights - only the Twilight Sentinel. Removing the "pop up" fuses, as you call them, is not a safe thing to do IMO, but you do you.
Just run mine during daytime for pride of driving. The fuse is always ready just in case. Check weather before taking my baby out. I look after my baby and it look's after me. Cheers enjoy.
 

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