Twilight Sentinel for 91-93 Caprice


Parts needed:


Twilight Sentinel Control module and harness.

Either an OCC or BRM headlight switch assembly that has twilight sentinel

OR if you look on the back side of the Caprice factory panel you can see where you can just as easily trim it out then all you need is the sentinel switch and connector w/wires.

Then you will need three female contacts to plug into body side connector at the sentinel harness and one female contact that will plug into the headlight switch.

3’ of orange, purple, light green 18 ga. wire



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Twilight sentinel switch has four wires on the connector.


  1. terminal is purple
  2. terminal is light green
  3. terminal is black
  4. terminal is black   


Remove the dash bezel to get to the headlight switch assembly and remove the undercover and skidplate.  Un plug the headlight switch and dimmer control and illumination bulb. Using the Buick/Olds headlight assembly (or cut the hole in the stock one) plug in the bulb (good time to check to see if its still working) and dimmer connector. Then slip the three wires thru the dash and up and over the steering column over to the right side of the column. You will need to add an orange wire and contact to the headlight switch connector in position E (the empty position), next to the existing orange you see. This and the purple and green wires from the sentinel switch will need to be connected into the harness where the Sentinel control module will interconnect with the factory harness, C220 in the factory service manual. Tie the two blacks together into a single lead and that will get soldered to the black wire on the instrument panel dimmer control. I left a little slack on that wire then about three inches from the connector stripped the insulation on the wire ¼ inch then soldered it.

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 This is located just to the right of the steering column on the dash brace. Once you have the undercover and skidplate out of the way look at the dash brace for a black connector and a white connector that should be snapped into the brace. If it’s like mine the factory didn’t bother and they are just laying to the right of the brace. Unhook these from the brace and pull down where you can disconnect them. When you look at the sentinel male white connector you will see the purple, orange and green wires  but not on the dash harness side. This is where you will need to connect them into the dash harness. Cut the three wires to suit your liking and solder on the pins.

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 Push out the gray contact retainer by pushing it from both sides of the connector, once its out then you can snap in the three wires and contacts matching the colors to the sentinel connector then reinstall the retainer.

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Connect the sentinel harness in-between the dash harness and snap the black and white connectors back into the brace. Slip the control module up and around the dash harness and secure it. I used a large tie wrap around the harness.

Once I removed the defroster grille I discovered there was no socket for the photocell. I had to acquire a pocket from another grill and since I am going to add climate control I drilled the hole for the ambient sensor in the grille while it was on the bench. I bonded the pocket onto the grille with 2ton epoxy and tossed in the wife’s oven for an hour so I could keep working.

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Hard part was laying under the dash and pushing the photocell up far enough that I could reach it from the defroster opening. Third hand would make it easy.

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Twisted the photocell into its position and snapped down the grille. Start up the car and place your hand over the sensor and the headlights should turn on within a few seconds. With hand removed it took about a minute for them to shut back off. Put everything back together cause….. You’re done…

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