I've found a few older threads dealing with similar issues, but nothing exactly like what I'm dealing with. When I bought my '03 last February, I noticed that (with the heat turned up) I was getting cold air out of the driver's side vents, but hot air out of the passenger side vents. Now that it's cooling down in Tennessee, I need to address the issue before winter.

My truck is an '03 Limited 4wd v8... I've fooled around with the settings, and am getting the following issue: With the climate control turned up to 80 or "Hi", I get really hot air coming from every vent/floor vent/defrosting vent to the passenger's side of the center console, vent on the driver's side blows cold air, like COLD air. Where it really messes with me is defrosting, since I can't defrost the driver's side of the windshield because of this.

I've read some things about cleaning or replacing the heater core, but I'm leaning more towards a stuck blend door somewhere, since the heat is CLEARLY working on the passenger side. Is there a blend door somewhere that divides the passenger/driver "compartments". Any advice appreciated!