Driving into work this morning and noticed it was super hot in the cabin. Sure enough, I'm not getting fresh air through the vents anymore with the temp dial turned all the way to the blue. I got a bad headache too, so now I'm paranoid I might be breathing something in I shouldn't. AC was running fine all summer. Please help!

 

2006 Ranger

Fresh air vent is always open unless you have MAX AC selected on dash

What you are describing is no Temp Control, which is done with an electric motor operating the Blend Door in that cab
The Motor is called Blend Door Actuator, and a common failure in Fords after 1994

The Blend Door routes the air from the blower/fan either thru the Heater Core(HOT/RED) or around the Heater Core(COLD/BLUE), or anywhere in between to adjust air temp coming out the Vents
The Actuator moves the Blend Door, actuator is controlled by the TEMP **** on the dash

Google: ford ranger blend door actuator

There are several videos to watch to see if this is your problem