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If the AC is properly charged, the compressor is engaging, but you still get warm air I suspect the issue may be related to what is called a blend air door actuator. This actuator opens and closes a door to the condenser which is what gets cold and cools the interior.
If the door doesn't open to allow air to pass the evaporator, no cold air will enter the vehicle. Please keep in mind, I am suggesting this because you had the work professionally done and the system appears to be working.
Here is a link that shows in general how the blend air door actuator is replaced and explains common symptoms:
Here are the directions specific to your vehicle for replacement of a single zone actuator. The attached pictures correlate with the directions.
blend air door
2007 Chevy Truck Uplander V6-3.9L
Air Temperature Actuator Replacement (Single Zone)
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Removal and Replacement HVAC - Manual Air Temperature Actuator Replacement (Single Zone)
1. Remove the driver side knee bolster.
2. Locate the air temperature actuator (6).
3. Disconnect the air temperature actuator electrical connector (7).
4. Remove the air temperature actuator bolts/screws (1).
5. Remove the air temperature actuator (2).
6. Remove the air temperature actuator lever (3), if necessary.
Important: The actuator lever can only be inserted into the door one way.
1. Install the air temperature actuator lever (3), if necessary.
2. Install the air temperature actuator (2).
Notice: Refer to Fastener Notice.
3. Install the air temperature actuator bolts/screws (1).
Tighten the bolts/screws to 1.2 N.m (11 lb in).
4. Connect the air temperature actuator electrical connector (7).
5. Install the driver side knee bolster.
6. Re-calibrate the actuators. Refer to Actuators Recalibration. See: Vehicle > Programming and Relearning
Let me know if this helps or if you have other questions.
Images (Click to make bigger)
Saturday, August 10th, 2019 AT 7:36 PM