I have a 98 cadillac deville and my headlight dont work at night but day time lights work in daylight when i pull out switch for lights go off

SOURCE: 98 cadillac deville - brake lights won't turn off

Under the dashboard, near the top of the brake pedal on the back side, there is a switch, disconnect the wire, if the brake lights go out, the switch is bad, need to replace it.

SOURCE: 97 Caddy Deville--Headlights won't come on. Fuses OK

check blown body and / or lighter fuses 20A

SOURCE: 1996 cadillac deville-auto switches to econ when turning on air

i have a 96 DeVille that did the same thing. It means your coolant tank is almost empty. It switches automaticlly to preserve based upon temp readings.

SOURCE: 2001 cadillac deville theft lock on after replaced battery help!

IF when you purchased your car you didn't set your own personal code you will have to take this to your local GM dealer and they can pull the code that is set at the factory and unlock your radio.THe proceedure for setting your own code then unlocking radio is in your owners manual.The dealership I worked for did this for free.

SOURCE: 2001 Cadillac Deville problems starting

I have had the same problem and I have come to the conclusion it is the security system. After 3 minutes the car will start so there is nothing wrong with the battery or starter. I have had it to the dealer a few times and they cannot solve it. It may be the locks on the doors and they may not be resetting properly. I have learned to live with it.