Driver side blows cold air on all modes

Hi,

It does sound like the blend air door actuator. There are two on this vehicle. The right side is likely bad.

Here is a link showing how in general to replace one:

https://www.2carpros.com/articles/replace-blend-door-motor

Here are the directions for replacement. The attached pics correlate with the directions. Note that in pic 1, I highlighted the actuator.

_______________________________

2008 Chevy Truck TrailBlazer 4WD V8-5.3L
Air Temperature Actuator Replacement - Right Side
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Removal and Replacement HVAC - Manual Air Temperature Actuator Replacement - Right Side
AIR TEMPERATURE ACTUATOR REPLACEMENT - RIGHT SIDE
Air Temperature Actuator Replacement - Right Side

Removal Procedure

1. Remove the I/P carrier.

see pic 1

2. Remove the right side air temperature actuator retaining screws.
3. Disconnect the right side air temperature actuator electrical connector.
4. Remove the right side air temperature actuator.

Installation Procedure

see pic 2

1. Install the right side air temperature actuator.

Notice: Refer to Fastener Notice.

2. Install the right side air temperature actuator retaining screws.

Tighten the screws to 1.9 N.m (17 lb in).

3. Connect the right side air temperature actuator electrical connector.
4. Install the I/P carrier.
5. Recalibrate the air temperature actuator on vehicles equipped with automatic climate control (C68). Refer to Actuator Recalibration. See: Vehicle > Programming and Relearning
_____________________

Let me know if this helps.

Take care,
Joe