I have a 2004 Tahoe with manual dual climate control. The issue that I am having is that the drive side vents constantly blow hot air, all other vents blow cold air if selected to do so and the vents in the rest of the vehicle blow whatever air is selected. The defrost, floor and vent modes all work properly. It's just the driver side that blows hot. Looking forward to fixing this for the wife. Thanks in advance for your help.

 

It sounds like a blend door issue...

 

Stacy Green welcome to the forum...
I would agree, check the blend door for the passenger side...

You might want to try the re-calibration procedure to see if it resolves the issue...skip the part of installing the HVAC actuator as you are only going to reprogram the one installed ....

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

Alternate Method (w/o Scan Tool)
Clear all DTCs.
Place the ignition switch to the OFF position.
Install the HVAC actuator.
Connect all previously disconnected components.
Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
Install the HVAC/ECAS fuse.
Start the vehicle.
Wait 40 seconds for the HVAC control module to self-calibrate.
Verify that no DTCs have set as current DTCs.

 

Just to make sure I'm looking at the right part. The part that is in question is on the passenger side on the under side of the dash....and please tell this rookie what the heck DTCs are, lol.

 

DTC's are Diagnostic Trouble Codes , codes that would be set in the computer for a technician to read and assist in troubleshooting...
You don't need to do that at this point as you are just going to try and re-calibrate the unit to see if it resolves the issue...
I have reduced the procedure to what you can do to see if it resolves the problem...

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

Place the ignition switch to the OFF position.

Remove the HVAC/ECAS fuse for a minimum of 10 seconds.

Install the HVAC/ECAS fuse.

Start the vehicle.

Wait 40 seconds for the HVAC control module to self-calibrate.


I would give it a full minute to complete and then check to see if the door(s) are controlling the temp correctly.

 

OK, the reset/calibration didn't work. So what might be the next step. I'm being told two differing opinions about this tahoe having 2, an upper and a lower blend door, and that the top door would be the one to replace. I'm sticking with this forum though for the answer. Thanks again for the help.

 

I would suggest checking the electrical connections to the blend door next...
I have not had to service the HVAC system so I can only speculate on the accessibility. I would get under the dash and check the connectors for damage and try re-seating them...

I suspect the door motor is bad, I would still check the connections to verify that they have not been kicked loose or accidentally damaged...