1997 Ford F-250

Heater problem
1997 Ford F250 V8 Four Wheel Drive Manual 413000 miles

I am wondering if the cable connected to knob on dash is responsible for changing cabin temperature from cold to hot. I was working in Miami and am now in N. Ga. In Miami I was using the air conditioner, now that I am home I need The heater. Everything has always worked fine until now. I removed the glove box so I can see the heater box. The cable ends at the top of the box and appears to go into a little white " arm" on top of the box and recessed a little bit. When I turn the knob is this " little white arm" supposed to move back and forth? If so can I move it manually with a pair of pliers without damaging anything?
December 3, 2009.

If I was working on your truck, I would call my local Ford dealer with the last 8 digits of my VIN.
And ask him/her to fax me a exploded view of the heater parts.

Knowing how things go together, goes a long ways as far as knowing how they are supposed to work.

Dec 4, 2009.