TRYING TO FIGURE OUT WHY MY NOTHING IS COMING OUT OF MY VENTS WHEN I TURN ON MY HEATER, MY DEFROSTER IS THE ONLY THING THAT WORKS.

replace the switch its self.. you can search ebay motors under electrical and find one easily.. also they remove easily and just plug in the back..

does the car have automatic climate control?

It all depends on whether your truck is equipped with Automatic Climate Control or Manual HVAC. You could have a broken control head assembly a broken mode door cable, a failed electronic mode door actuator, a broken mode door, or a loose or broken wire or connector.

To put it simply, your mode doors are not swithching modes - the reason for this can vary depending on which system you have.

Sounds like the heater core is leaking coolant. If it is leaking it will blow steam out of defrost vents and fog the windshield. Symptoms: low coolant level in radiator, steam coming out vents when engine is warmed up, odor of anti-freeze coming out of vents, wet carpet in floorboard near heater blower motor.
If so, replace heater core.

Sounds like the flap valve in your vent system that allows air to go to the defrosters is either jammed or broken. Unfortunately you will have to take the vent system apart to look.

sounds like the vent flap is stuck

check the control knob it may appear to be working but is not turning the actual controller

With the engine off, radio too, turn the key on and try the heater fan on all speeds. No fan, check the fuses. Fan is ok, check the coolant level, if thats fine, then check for a mouse nest in the duct work. Frankster016

wow...here it is spring and no one answered either of you? Is there a large volume of air when fan is on high? Where is it going? Or do you not hear anything from the fan? The 240 has an awesome heater. On high it would heat a small home! If no sound, your blower motor is dead assuming the fuse is good. If you hear the fan blowing, figure out where the air IS going. Note that the only way to turn the dash vents off is with the white Oreo dials. To defrost, only that button should be pressed in and dash vents off. Behind the dash switches there is a maze of short vacuum hoses. Often times, people monkey w/ these and reconnect them incorrectly. Haynes manual or Chilton's have proper diagrams. It could be that the vacuum hose coming from the manifold and entering the firewall is split on the under side and not visible, also.