Haynes has an excellent repair manual for this and any vehicle. It contains diagrams as well as how-to-do references. It costs about $20, and is available at most auto parts dealers. The ISBN is 1 56392 321 1.
If you look under the dash by the brake petal there is a fuse box and a diagram is on the cover of it.
www.autozone.com has the info you need under their repair section.
The battery for the Buick LeSabre (2000) is located under the rear seat cushion.
On my 1994 Lesabre it is under the dash about center at edge of carpeting
Under the back seat
its under the back seat
You can find the wiring diagram for the air conditioning on a 1992 Buick LeSabre (Limited/Custom) at your local auto parts store (Pep Boys, AutoZone, Strauss Discount Auto, Napa Auto Parts,Advanced Auto, etc.) look or ask for the "Chilton" auto repair manual titled "FULL SIZE FWD Buick" the diagram is in the back of the book. ***Note if you were planning on OPENING any air conditioning lines, the system in under very high pressure and this should only be done by a Certified/Trained a/c technician. Otherwise, hope i helped. :)
Under the back seat.
its under the back seat
the battery is under the back seat
If it is like the 2000 LeSabre, the rear seat will lift out and the battery is under it on the passenger side. It requires some force, but the front of the seat cushion should lift up then can be removed.
Under hood diagram or autozone.com