Back floor on passenger side is wet

PWR WDO - 30amp circuit breaker , DRV -MDL 10amp fuse - both are located in the rear fuse box .
Fuse Block Rear
Under the left side of the rear passenger compartment seat

is your passenger side floor board wet? is so its your heater core. if not i have no clue what to tell you

have you checked for holes in the floor. the shock towers rust on those. I had a 1995 that had rust in the truck floor next to the rear seat

Wet floors and carpets are usually a sign that the drain tube outside is plugged up. The tube is usually in the engine compartment at the bottom of the firewall where it joins the floor.
If you are saying the air will not come out the floor or defrost you may have a faulty blend door under the dash.

Your heater core has sprung a leak. This is about a 6 hour repair. Look for a reputible shop locally to do this. The part cost is roughly 80$

Your heater core, which is located under the passenger side dash, is leaking.

it's under the back seat in the passenger side. the driver side houses the fuse box.

It is under the back seat on the driver's side in the 2000 LeSabre.

drill a samll hole in floor for drain

fault temp sensors
still can be a worn or stuck shaft flap at the actuators
or actuators is still faulty