Buick lesabre 2000 head lights won't shut off

You should have a wiper fuse in the interior fuse box that you can pull to temporarily turn the wipers off. I suspect that the issue is due to a bad wiper switch which will need to be replaced.

check all fuses and if that isn't it then tap into another power source of the same amperage rating

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 ?

You have a blowin head gasket, Verry costly to have repaired, Plan on $2000 end up.

O2 Sensors only reads Oxygen Content in Exhaust
Converter,so forget that persons advice in the future

The O2 Sensor info is for adjusting fuel trim or injector
pulse timing,not your problem

You change front upstream O2 sensors at 100,000
miles, as preventative maintenance

Check Fuel Pressure at motor & pump maybe failing
as well,doesn't hold pressure thus takes too long to start

Clean the Air Idle Valve on throttle body & it won't shut off
at stops

USE A SLIM JIM TO POP THE DOOR RELEASE CATCH FROM THE OUTSIDE, THEN ONCE OPEN, REMOVE THE DOOR CARD & REMOVE & REPLACE THE DOOR SOLENOID

Have 2000 Buick Lesabre custom every time car gets up to operating temp. the engine misses going down the road , also let car sit and idle and it shuts off after about 2 minutes , my code reads PO171 system to lean bank 1, changed co2 censor, mass air flow censor, plug wires, and plugs.

To the taillights work, as well as the signals, and break lights, do the high beams work..check To ensure the connections to the headlights are not corroded and secured otherwise switch may be faulty. Start with that first as well as check all your fuses.

I used a knife to pry the button up when I did the same thing. Also make sure all the buttons are up!

they have had alot of problems with key switches in that model that is where i would start