Q: Dual zone heat. Driver side blows hot, passenger cold. what is issue? on 2013 Ford Explorer

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I have dual zone heating/cooling. Driver's side blows hot air, but passenger side, just cold. Car has about 105,000. What could be issue & how much labor involved to fix?
(1) Answer
Likely you have a bad blend door on the passenger side.
With dual zone A/C and heat, you have extra mode doors, and blend doors, that force the proper temperature air into the proper vents. When these fail (often), your situation is replicated.
This happens in enough vehicles that there are kits out there to avoid removing the dashboard to change the doors. However, if you only have one of the door actuators bad, then you may be able to change it without removing anything else.
Let me know what questions you have, and here is a link in case you prefer to have it diagnosed: