I think my blend door actuator is going out
 

Whenever my A/C is turned on, it blows nice cold air. As long as the blower is on "1", "2", and sometimes ", it blows cold air. If I turn it to "4" I can hear a small "thud" behind the dash. It sounds like the blend door is shutting. All my functions work like they should. I think the actuator is goin out and isn't pushing the door all the way closed, and when I turn it to "4" it pushes it te other way. What do you all think? Please help! :)

the blend door is a varialbe positoion, electric motor control door. It does not "flop" back and forth. It stays in one position to control the air temp by mixing hot and cold air. If you have good temp control, then its fine. If you can not control the temp, then you have a problem.

Well I have the temp control knob all the way in the cold position. Would it be possible tht tht actuator doesn't have the "umph" it needs to fully close in that position? I know it stays in one position, I'm just wondering if it were going out would it not quite reach that full position?

Your blend door may be broken. Common problem. The whole dash has to come out to fix it though and you may as well replace the heater core whole your in there. See if the air temp changes when you accelerate from a dead stop and if the it again changes when you brake to a complete stop. If so, it's a broken blend door. Big job to replace it.

Unless I go with HeaterTreater right? Haha! Alright I'll try that. I hope it's the actuator. Cause I don't feel like pulling the dash or cutting any holes in my heater box. Lol. How much of a chore is it to change a heater core?

Once the HVAC box is out from behind the dash, a panel on the box can be removed to observe both the heater core and the blend door. I've seen that "heater treater" video, repairs (if you can call it that) don't get much cruder than that.