Heater and A/C controls all work, but the temperature of the air blowing through the ductwork is always ambient temperature. A/C lines under the hood get cold (condensation forms) when I turn on A/C controls, so I believe A/C is working. Why can't I get warm or cold air delivered into the cab?

 

dunno what year truck you have but vacuum motors control the flow,I believe.A friend also had the temp control on his Ranger go bad,so meb'be that's it.

 

I have a 1998 F-250. The vacuum motor works on the Blend door. I can't tell where all the other vacuum lines go without taking the whole dash apart.
The temperature control **** resistance varies from 300 ohms to around 5000 ohms.

 

Problems fixed. Turns out I had the Blend door confused with one of the damper doors. The Blend door was broken.