rear climate sometimes works sometimes dont

[TrailseekingTB]

I searched forums hopefully I tried all search options and terms. But I've noticed that my rear doesn't wanna blow sometimes. Ill turn it to 3 up front in the knob( or to rear control and control it from there) and I can hear the blower in the back turning. But no air or heat. Noticed it works more when im sitting still in park. Idk if there is some type of trap door situation that when I start driving falls shut??? But its kinda weird. Pretty annoying when I got cold friends and family in the back driving down the road and it doesn't work too!! any one got suggestions?? Thanks! And again I searched for this and didn't find it I hope I havnt started a topic already been discussed. Thanks

[DirtyBacon04]

You might wanna try a topic like that over at GMTNation

[TrailseekingTB]

You might wanna try a topic like that over at GMTNation

Ok, thanks I love all the help I get here so I thought I'd try here first.