AC control is going crazy

Help. lol This thing is going nuts. 2003 Tacoma SR5. When I turn the AC to cold the actuator just under the dash towards the front goes slap nuts.

When you look at it it appears to not have its mind made up on whether it wants to open or close. Of course if I put it all the way to heat it works fine. I used to be able to open to heat then slowly take it back to cold and it would stop.

That is no longer working. Does anyone know how that thing works? Appears electrical and not vacuum. Would I probably only need to just change the part under the dash or possibly the control behind the temp knob. It opens and closed just fine with the know, just goes crazy and is fairly loud as it psychotically opens and closes when on the cold side.

Thx!