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Odds are it is a faulty blend door actuator, its also possibly the blend door itself or the climate control panel.
You need to perform some diagnostics from Ford prior to replacing anything.
Download the self test and symptom chart and pinpoint tests and component tests by clicking HERE
Download the blend door access and replacement HERE
Let me know if you have any difficulties doing these tests.
The car is at operating temp when doing this test correct?
The passenger side is putting out alot of heat when on the manual settings when doing this test correct?