Had a strange experience on our MKC yesterday. Started the car. The driver's side vents blew very warm air, the passenger side blew cold air. I had to drive with this for about 4 miles.
To correct, I turned the AC on and off. Put on MAX AC. Turned the car off and let it sit. When I restarted the car, the problem continued. Finally, I switched to defrost. That fixed the issue when I switch back to AC. Both sides of the vehicle vents blew cool air.
I'm guessing an air blend door stuck. I'll be watching for this in the future to see if it needs to be fixed.