My heat only blows through driver side and blows cold on passenger side why is ?

Hello, Your vehicle has small doors inside the air ducts that are driven by small motors outside ducts. When you request cold or hot air, the blend doors change position to change the temperature of the air that is allowed to the vents. The blend door actuators fail commonly on many types of vehicles, and these are the little motors I mentioned that open and close the blend doors. You must check your fuses first. I bad fuse will cause blend doors in the ducts to fail, but the most common repair is replacement of the actuator. Be warned, some vehicles require the entire dashboard be removed.