Air conditioner started blowing hot air

Either AC compressor or AC clutch failure or both highly likely as Kia Sedona has notable history of this

Sure, one might trace the wire that connects to the compressor, and while its challenging to reach without removal of both fans, it does follow upward into the engine wiring harness. At that point its much more convenient to push a needle into the wire and connect a meter to it to see if it is energized when AC selector on, cabin fan on and cabin thermostat set to coldest setting.

If no voltage then check fuses and try swapping idential relays in the engine compartment box to be sure. If voltage present, then assume the worst.

More important is why the failure. I'm convinced a design error by Kia relative to the suction or low pressure hose is the root cause of such frequent AC compressor or AC clutch failures. You can buy a new Kia OEM suction hose, position it for to install and observe immediate kinking and or collapse. Kia has likely long been aware of this problem but never conducted a recall. You can solve it permanently, toss your existing suction hose and buy this one: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=181880844799

If you buy a "Tough One" brand replacement compressor and filter/dryer together from Advance Auto Parts it has a lifetime replacement warranty. No other compressor is sold with a lifetime warant for a Kia Sedona, not even from Kia itself.

Your a/c compressor is not working.
you have to have the system checked by an air conditioning place or the dealer as to what the cause is.