Why does your 2010 Ford Taurus blow hot air on driver side and cold on the passenger side when dual climate control is off?

The issue of your 2010 Ford Taurus blowing hot air on the driver side and cold air on the passenger side, even with dual climate control off, could be due to a malfunctioning blend door actuator. This actuator controls the flow of air from the heater core and may be stuck or faulty, causing a temperature imbalance. Additionally, there could be a problem with the HVAC control module or a blockage in the ventilation system. It's advisable to have the system inspected to identify and resolve the issue.