Only the heat works when air is on high? Odd pop noise?

[hockeyadc]

So when I have the air on 1 or 2, it comes out cold. However as soon as I put it to 4, some times 3, a "pop" noise is heard, and it goes full heat. I have to turn everything off, put it back to one, and put the cold/heat blend all the way to cold and wait a while until I can get cold air again on settings 1 or 2.

Any idea what is going on here? I've replaced the blend door actuator twice so I have no idea what it could be. I was thinking the blend door itself, but why would it slam shut to the heat setting? I thought only the cold air would work if the blend door was broken?

 

[apenland01]

I would just keep searching the actuator threads, because there are a few different things that will cause this. I think all of them have been solved, you just need to find the one that is closest to your issue.