Headlights flicker on and off at night on my 99 buick lesabre

If you have the twilight sentinel system, the relay is stuck.

Three possibilities. The fuses, the light switch, and the turn signal switch. Most likely the light switch, because the others have different fuses and run from different spots in the TS switch.

On a 1990 Buick you have a fuseable link between the headlight switch and the battery.
Do you have power in and out of the headlight switch and the dimmer switch ?

Click here to see probale cause.

I woukld suspect the headlight switch is defective and the connector to it is burnt, a common problem in this year.

It sounds like they are automatic lights and that the light sensor is going bad. Look around on the dashboard for a small plastic dome, that is where the sensor is. There should be a plate or something holding it in place.

Your high beam switch is bad most likely.

Traction light is on because the abs is on.Traction control needs to have the abs system fully functioning to work.Most common cause of abs light is a wheel speed sensor.As for your lights flickering the alternator may be going out or you have a poor ground connection.Would check battery cables first to make sure they are tight.

The regulator in the alternator is most likely the problem.
The alternator could be charging.......just not correctly....... the flickering headlights are showing a varying voltage.......and with the charging light flickering too..........99% chance you need a complete rebuilt alternator.

there is a short somewhere you will have to remove the dash and investigate