Fan on drivers side will not turn on, passenger side fan working

Your Taurus only has 1 blower motor for the Heater/AC. Are you talking about the engine cooling fan?

No, I'm inquiring about the fan that blows out the heat or AC, there is a driver side and a passenger side that you can regulate, it was working last week now only the passenger side is blowing the heat. Thanks for your assistance

Ok, I think I know what you're talking about. You have a Dual Zone Heater/AC system. I'm correct in telling you that it only has one blower motor. What you are experiencing is a failure in your Left side electric Mode Door Actuator. It isn't opening to allow airflow. It's a little tough to get to and about 1.5 to 2.7 hours of labor to replace (working upside down under the dash). Procedure: The LH temperature blend door actuator can be accessed from below the LH side of the instrument panel. Remove the 2 LH temperature blend door actuator screws. Disconnect the LH temperature blend door actuator electrical connector. Remove the LH temperature blend door actuator. To install, reverse the removal procedure. NOTE: The purpose of the module actuator position calibration is to allow the HVAC module to reinitialize and calibrate the actuator stop points. To carry out calibration, carry out the following steps. Remove Smart Junction Box (SJB) fuse 15 for at least one minute. NOTE: When the ignition switch is switched to the ON position, the HVAC module will initialize and calibrate the actuators. Calibration of the actuators will take approximately 30 seconds. Reinstall SJB (Smart Junction Box) fuse 15. Turn the ignition switch to the ON position and wait 30 seconds before verifying correct LH temperature blend door operation.