2013 Lincoln MKX Hot one side, cold the other

Drivers AC HOT / passenger COLD

Simple things first - with the car running, turn off the HVAC system, turn it on, and push the ‘auto’ button. If that doesn’t help, you may have a problem with how the doors are being controlled. Me, I’d take it to my dealer.

No need to take the vehicle to the dealer for this problem. It’s out of warranty.

An independent shop can figure out why the blend door isn’t working on the drivers side.

Tester

Try adjusting each side all the way to coldest and back to hottest and they n may relearn . It works on my Chrysler, couldn’t hurt to try. There is most likely a calibration procedure for the mode doors that can be found on the internet. You also may have a bad actuator.