Leading edge of the car will have more pressure. This is also where the inlet of the HVAC is located. Open a window and now that high pressure has somewhere to escape, instead of going around the bubble that is the cabin...

 

On most A/C systems from demestic vehicles, if you have the controls completely turned off, there should not be any external air coming out of the vents regardless if you have the window up or down. The dampers, blend doors controls airflow entering the cabin and where. Once they are properly shut, no air should come out of the vents.

Some imports have a separate air control switch. (external or recirculating). If you put it external, then you will get external air coming thru the vents even if the a/c controls are off.

 

So then the 'breathing' sound I hear coming from my dash would be the control for the blend door?

I know that when I use the defrost that the ac gets involved so that is why I hear this sound when either ac or defrost is run...and get only hot air

so to correct this, you say the whole dash needs to come apart? that would sound like a dealer chore...sheit!

cheers

 

Correct, you will have to go see a dealer or a mechanic you trust to tear down the dash. Luckily for me, I have a close friend that is a mechanic with his own shop and watched him tear down my Durango. It was a 8 hour ordeal from start to finish. My heater core went out just after my warranty expired at 37k. He was nice enough to only charge me a couple bucks but I had to pay him a least a couple hundred more. Dealer wanted at least 600-700 bucks in labor to tear down the dash. After watching my friend do it, I am glad I did not do it myself, don't have the patience and no way can remember where all the screws go back to. Too much things to remove simply to gain access to the heater core. Wished they made a removable panel at the engine bay side of the firewall to remove the core!

 

Wished they made a removable panel at the engine bay side of the firewall to remove the core!



If they did that then the stealerships would riot in the streets.