I have a 1998 buick century with auto-on headlights - how can i turn off the headlights while the car is running?

There's this website www.reliable-store.com
They have books on ALL vehicles.
it covers wiring diagrams, electrical diagrams,
fuse diagram, torque specs, PCV, error codes, fault codes, service info,
repair info, parts info, owner's/service/repair/parts/maintenance manuals etc everything totally..
I have 1987 toyota 4runner model and I keep servicing and when needed repair it on my own. worth it !!!

drivers side behind headlight assembly 4 clips holding top cover on

The Buick Century is equipped with a multi-switch. This switch is an all in one switch that controls your cruise control, windshield wipers and turn signals in one switch. This switch also controls dimming and brightening of your headlights. The dimmer switch is simple to replace, and all you need is a phillips head screwdriver to complete the task.

1. Removing the Steering Column Shroud
   • Removing the dimmer switch starts at the steering column. To plan this task out, access the steering column by removing the screws holding the steering column shroud in place. This will expose the turn signal lever. Remove the lever by twisting it forward, and pulling it out of the switch.
     
   Removing the Dimmer Switch
   • The switch is held on by two screws and a wiring harness. The wiring harness can be removed by prying up on the locking tabs and pulling the connector out of the socket. The two screws can be removed with a phillips head screwdriver. The switch will slide out. To install a dimmer switch, be sure to repeat these steps in reverse order.
     

take it to a auto center to have the check engine light turned off. It will need to be done with a OBIII scanner

I suspect the headlight relay has failed in the closed position. You should be able to buy a new headlight relay for around 10$ at a local auto-parts store. I'm not 100% sure where the relay box is located in a 1998 Buick. However, usually they're made out of black plastic and located in the engine compartment. Typically the box has a snap-on lid. Most of the time the relays are labeled, or there might be a diagram in your owners manual. Unplug the old headlight relay by hand and plug the new one in. I hope this advice helps you out.

is it HOT or just not as cold. If its HOT, like heated air, there is a door problem, if its just not cool, the a/c refridgerent is low and will need a recharge, most likely the comp is leaking.

CHECK YOUR TAIL LAMP/ILLUMINATION FUSE, YOUR TAIL LAMPS & DASH LIGHTS ARE ON THE SAME CIRCUIT

have you tried with the light switch pulled out or are you using the auto selection?

At my shop we have a product from Ever-Wear, it is a headlight restoration kit, do it on the car and works great. Did one light on my car and left the other one foggy as a demo. Great Product

Gently tap the base of the mount upwards. I just replaced mine and I thought there was a cover over the winshield mount, turns out it is just pushed on to the wedge that is mounted to the windshield. Good Luck, webree