Outside. Anything you do to the inside will restrict air flow.
What I think you are asking is how to you set your AC so it stops drawing in air from the outside, which is humid and not very cold even after the AC, and instead recirculates the air already inside, so it gets drier, and therefore gets colder each time it passes through the AC. Somewhere on your heating/cooling control panel you will have something that looks like a car with a circular arrow meaning "circulate the air" or you will have something that says "recirc" or something like that, or maybe you don't need one because when you turn on the AC it automatically goes into recirculation mode.
Usually stamped on the outside of the handler.
A/C uses outside air, while max A/C recirculates the inside air and runs at a higher fan speed
but what if the ac gets frozenSure ... once the thermostat senses the cooler air, it will shut down the AC unit anyway.
The purpose of an AC filter is that they keep the inside of the air conditioner clean by trapping dirt particles and the keep the outside air clean by sucking in dirt particles.
MAX A/C position recirculates the air inside , shuts off air from outside
On the passengers side locate the a/c blower motor and then look up, you will seen the recirculating door and to the left of that you will see the actuator that controls the the inside and outside air.........
An air filter resides inside the air return for your car, usually inside the dashboard. This filter should be changed about every 2 years, or sooner if it gets clogged.
Sounds like your system is a heat pump. When a heat pump cools in the summer, the inside coil gets cold and the outside coil gets hot. When the heat pump heats in the winter, the inside coil gets hot, and the outside coil gets cold. It sounds like your heat pump is stuck in heating mode. Check your thermostat to be sure it didn't accidentally get switched to heat. It could be the reversing valve inside the unit is stuck, or an electrical control is broken, forcing the reversing valve to stay in the heating position. Perhaps a call to the serviceman is in order!
The inside fan blows air through the ac coils to cool the air. It should be on a separate breaker or fuse circuit from the outside unit. See if there is a fuse box on the side of the inside unit and check the breakers in the house main breaker box. Also stand quietly beside the inside unit and listen for the fan motor running. If the motor is heard running then either the fan drive belt has broken, or the ac coils are clogged preventing air from flowing.
If you switch to "MAX A/C" for your air conditioning that will recirculate the air inside your Explorer , while shutting off the outside air that usually comes in for ventilation