I have a 2013 impala ltz. I believe an actulator is going out, but I just want to ensure I know which one. Whenever you open a door it starts to tick like a mad man. Also, whenever you switch vents it ticks as well, switching to hot/cold makes it tick, and the passenger side ac/heat doesn't always switch. I'll have it max on heat and its ice cold, so I have to go to cold then back to heat for it to switch. Inlet actuator or the blend? Easy to replace?