Alright so on my 06 1500 slt I can have the heat on full blast on the floor and face setting it blows extremely hot air but on really cold days I can feel the cold air rushing in on my feet so much that if I put my dunkin donuts coffee cup in the cup holder once I get to work after a 20 min ride it's cold. I can feel the hot air on the floor but cold air out powers the hot. Not to mention my girlfriend is ready to sit in the back because the passenger side is colder on the floor then drivers my face will be melting and she will be freezing cause so much air seems to be rushing in. Any ideas what could be causing this? Thanks for any advice.

 

Usually if there is a differance in temperatures it could be caused by a partially clogged heater core. Remove the heater core lines and back-flush them with a garden hose. Re-fill the lines, reattatch, and fill the rest of the radiator and hoses up. Make sure and bleed the system when you are done.

You may have another issue as well. There are foam pieces inside the dash that go around the vents. I dont have a picture, but if these get damaged it will allow air to rush in from the outside, even though the heater is working as it should. This is a pretty big fix as it required you to remove the entire dash.

Try the flush first and go from there. It should at least even out the temperatures. Good luck!

 

Yours is an obvious case of a broken recirc door. This is the door that determines weather you condition fresh air, or, recirculate cabin air. When this door breaks it allows the fresh air taken from the cowl to enter the cabin directly behind the glove box. And at highway speeds that air is under pressure, and can really pour in. You need to replace that door. visit heatertreater.net for more information. There are also tons of threads on this right here. Do a search for recirc door.

 

66three83 is bang on.
I just completed this a few months back for the same reason.
Used the Heater Treaters solution.
There's a video on their web site on how to diagnose and repair this.
Hope this helps?
Al.