Remove the old terminals, a large pair of bolt cutters or a hacksaw should get the job done.
Strip the ends of the wires with a knife and check for corrosion which will be black or green.
If there is corrosion you need to replace the cables.
If there is no corrosion replace terminals with screw on type for convenience or use solder on type if you prefer.
For screw on just put the cable in the terminal and tighten the screws.
For solder on you will need to to hold the terminal in vice grips and heat it with a torch and feed solder into the terminal while the terminal is hot. When the terminal is mostly full slowly dip the cable into the solder and hold there while you remove the heat. You now need to hold the cable perfectly still in the solder for about a minute or the solder will crack while drying and you will have a poor connection.
Reconnect terminals.
The battery is under the back seat
under the rear seat.
Replace the gasket.
Put a new battery in my 2001 quick lasabre and now my radio won't work
check the voltage regulator
no repair.... must replace.... $10 US at any parts store
location of the heating thermostat for the 99 Buick lasabre
Lift up rear seat & replace battery
where is the fuel pump switch located for a 1992 buick lasabre
Dead battery? Loose or corroded battery cables? Wire disconnected at top of starter?
In my 2000 LeSabre, it's under the back seat. Remove the rear seat and I'll bet it's there.
they had corrosion problems and mounting screw problems but what is your question?