You have A/C Must be nice!!!!

Well I know in my 74 runabout, the heater is controlled by a cable the runs to a flap the deverts the air to where it needs to go.

Im sure you have to have duct work that pipes the air I would first track the pipes down and find where it leads to the fan and in doing this you will find your problem or misdirected air flow

Should be vac controlled, check for vac leak or bad check valve or leaking vac tank/reservoir.

I have a 76 wagon with A/C and it used to work great now the air only blows out the windshield defrost vents. My question is are these cable controled or vacuum? and where do I start looking to find the problem?    Thanks for any info. al

Cars with AC have vacuum controls to direct where the air goes. (the temperature is cable operated)
Its designed to 'fail safe' if vacuum is lost-  the output goes to the defrost outlets so your windows don't fog up and possibly cause an accident.  Pretty good thinking IMO!

I had to remove the entire control unit to get access to mine.

Yes, do what B-N said.

Also, if you had work done to the car recently someone might have pluged the "exhaust" tube, or it might be clogged. For the vac. controls to work properly, there needs to be a 'bleeder' to release the vac. or you would not be able to change anything. The exhaust tube should have a small square rubber block on the end. Ford put it either under the hood or in the right side fender to keep you from hearing it hiss from inside the car.

Bill