You didn't mention if it was a car or truck and what series. About the only 2 possibilities are the heater core or windshield.
The floor in front of your seat where you place your feet.
that the floor is wet
Heater core under dash and console leaking
Heater core failure.
You have a leak. Possibly the drain lines are stopped up or the leak is at the windshield.
when they changed the heater core on my durango they didnt attach the air conditioner drain back up and it ran through my firewall so it caused my floor to get wet
wet suit, wet paint, wet floor.
... VIN Plate Location: Driver Side Front Floor:
Place a white towel on the floor of the car if when you press it down on there and the liquid is green its coolant leaking into your car it could be coming from a hose or your heater core
On a 1997 Ford Explorer : The toe board is the angled piece between the floor and the firewall in front of the driver and the front passenger
Friction is reduced on a wet floor.
i belive it under driver side floor on frame railup towards the front