Heater only heats on pass. side, cold air on ds. The front ds act. doesn't turn when going from hot to cold. I have three act. in all. Any one know exactly what this part is called. How can I tell which one I
need to order?

https://www.rockauto.com/en/catalog/...actuator,10721

01 buick lesabre limited

 

Seems like several of those actuators are the same GM Part Number? Iin any event, if they have not been changed, there should be an 8-digit GM Part Number stamped on them.

DO NOT test the new actuator before it is installed! That can cause internal issues with the new actuator.