There is an actuator under the dash on the drivers side of my new to me 2003 silverado that keeps moving the plastic piece its attached to back and forth all the time. Is this caused by a bad actuator? it looks like it only moves it an inch each way. Do I just need to change the actuator or what? It seems like the a/c and heat still both work fine so im not sure if this is a blend door that the actuator is connected to or what. It does go to some thing in the HVAC duct system.

 

If it's cycling continuously (popping) it's probably a defective actuator.

 

I couldn't see a part number on the actuator how do I know what actuator to get

 

Mine did the same exact thing. I replaced it and all is good

 

It's your mode actuator. Ask a parts store for it.