Heating/Cooling - Control Valve or Blend Door Actuator

2001 Tacoma, xtra cab, V6, 4wd

I have been dealing with a heating/cooling problem off and on for about a year and a half. When the dashboard control knob is turned from one extreme to another it tends to result in a ticking/grinding noise. The source of said noise is the motor of the actuator near the passenger foot well. The actuator is obviously struggling to move through the cycle into a new position. It tries for 10 seconds or so then stops without the temperature changing. I've narrowed the problem down to three possibilities. The actuator motor, the wire that runs from the actuator to the control valve, or the control valve.

The actuator seems to operate normally when it is detached from the wire. But having never operated it prior to my current problem I don't know what "normal" should be. The blend door seems to operate and close with ease when I move it manually. The wire seems like maybe there is mild resistance within the housing tube, but again I have no basis for comparison to its state prior to this problem.

*It is my understanding that "control valve" and "blend door" refer to the same part. Can anyone confirm?

Has anyone experienced this with their vehicle? What was your problem and the fix? Is the motor getting weak with age? Is the control valve jammed? Is there gunk inside the housing of the wire.