Cannot change temperature selector will rotate (from cold to hot), but will spring back when released

check cable adjustment and blend door it could be off or jammed. Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

Thank you for this, but was hoping you might expand the context. I have no idea where this item is relative to anything else. Is there a source of installation drawings I might access?

Disconnect negative battery cable. Remove 2 screws from cup holder and remove cup holder assembly.
Remove 2 screws from ashtray and remove ashtray. Carefully pry bezel away from instrument panel to disengage clips. Unplug connectors from cigarette lighter and auxiliary power outlet.
Remove 4 screws attaching heater control panel. Pull control panel rearward.
Disconnect wiring harness and vacuum connectors.
Push inward on Red cable connector to release connector.
Remove cable end from heater control panel.
Check cable ,check door operation in the heater box
click on the image to enlarge and to see cable adjustment

I finally had a chance to look at this in detail and found it just as you described. Once I got everything apart, I saw that the panel end of the control cable had kinked (short of its guide sheath) and was bunching up every time I tried to move the ****. I attempted to straighten the cable with pliers and succeeded only slightly, but apparently enough that the heater door now opens and closes when operated slowly. Regardless, if the problem recurs in the future, I'll know how to fix it (for the one or two times a year I need cabin heat here in Arizona). Thank you for your time and detailed reply.