Headlight sensor?

Where is, or what determines when your headlights turn on when it gets dark? And, is it adjustable? It has to get pretty dark before my headlights automatically turn on.
1990 SC 5SPD.
Is it part of the auto dimming high beam sensor on the mirror?

I don't think it has anything to do with the highbeam dimmer sensor. I have tried covering mine up and my lights didn't come on, but when they are on if I cover up the sensor, the highbeams turn on.

I don't know where the headlight sensor is located, but I am very interested in finding out as well.

On the early models the autolamp sensor is located in the dash about center of the steering. It is behind the 3 slot opening that is in that small dash panel just behind the gauge cluster. If you stand outside the car and look down through the windshield, you will see it very easily.

It is non adjustable to my knowledge. I would imagine someone with a little electrical know how could open it up and change the settings.

The autodim on the mirror is a separate sensor.

adjusting the auto-on and auto-dimmer

according to the manual... the auto-on is adjustable by the level you put it at. if you barely turn the setting on, just above where it clicks, your lights will turn on when it is dusk. If you raise it to max then it will wait until it is very dark to turn on and will remain on longer after the ignition is turned off.

For the auto-dimmer, the lowest setting will switch from high to low and low to high beams less. In the max position it will be most sensitive, picking up brake lights better and other white lights.

Personally I keep my auto-on settings at the min. and the auto-dim settings at the max.

Finally got home and looked at the manuals to get the real answer! The headlight on/off time for outside lighting conditions may be adjusted by removing the photocell from the dash and turning a small adjustment screw on the sensor. To make them come on earlier, turn it clockwise, to come on later, turn it counterclockwise. Not too much though,. The 89 manual says 1/8 turn is a five minute timing change. The 90-91 manuals say 1/16 turn is 15 minute change.

To get to the photocell just pop off that left side plastic defroster panel on the dash. It has four clips. The photocell sensor is under that and held in with two screws.

The lamp delay thumbwheel must be clicked "on" to activate the autolamp headlight on feature. Any movement of the wheel after the "on" position only makes the lights stay on longer after the ignition is turned off, it does not affect when the lights come on or go off according to outside light conditions.

As a side note, only the 89-90 SCs had the autodim (of high beams) as an option.

Thanks George and everyone.
I was on vacation last week and so it took a while for me to check responses. There are so many brains that visit this site, I don't think I've seen a question yet that someone didn't have an answer for. Makes looking after these cars a whole lot easier.