2004 Buick Century

There is a sensor to turn down the dash lights at night time

Where will I find this sensor?

Dave

typically, the switch that turns on the interior lights also dims the dash lights.

yes its a black **** to the left of the steering wheel on the dash.

Or, are you asking about the sensor that does it automatically?

Yes, the sensor which does it automatically

Should be on top of the dash.

It'* under the winshield defroster vent. Once you get it off It a small blue circle or a small black plastic egg like stucture that is about the size of a dime. It just pulls out with your fingers or a needle nose plyer. You can get them from the junk yard almost for free. Gm charges about $60 at its Stealerships.