My 2005 Tahoe is blowing warm air out of all the vents (what ever the temp is outside). The passenger and driver vents were periodically blowing hot air. I change the blend door actuator and it did not resolve the problem. I had the HVAC system checked and their are no leaks, the compressor is working, and the system is fully charged. They did indicate that the issue was with the Climate Control Unit. My question is how do I know it's trully the Climate Control Unit and not with the Mode Actuator. There are three actuators (Passenger, Driver, and Mode); I've changed the driver side.