No air through vents temperature problems

Hi Wicked513,

Just so I am clear. Your air only comes out on the defroster no matter which position you select? Also, it only blows cold unless you go to 85 degrees?

I am going to assume based on the you described your system that you have automatic temperature control and not a manual system.

If this is the case, unfortunately, I think we are going to need a scan tool to monitor a couple things. First we need to monitor what the different duct temp sensors are reading. It sounds like one of the sensors are not reading properly which means it throws off the systems ability to regulate the temperature.

The issue of it only blowing on defroster could be related to these sensor issues but again we are going to need to use the scan tool to command the distribution door in each different position. The scan tool makes the system ignore all inputs and moves the door if it is able to. If it moves with the scan tool then you know there is a sensor issue causing it to blow on that setting. If it does not move with the scan tool and stays on defrost then you know the actuator just isn't moving and more than likely has failed.

Either way, we need a scan tool to properly diagnose this one. Your vehicle is new enough that each of these systems are controlled by modules that operate based on what the input sensors are telling them.

I included the procedure to replace each of these suspected components but also an overview of how the system communicates to better illustrate what is happening.

Let me know if you have a scan tool or access to one that can monitor these sensors and command the door positions. Thanks

Okay. Unfortunately this doesn't change the need for a scan tool to run through the operation of the system. In fact, it strengthens that need because if I were going to guess, it sounds like the HVAC control module is the issue. That is purely going from experience with these types of issues but I want to stress, this could be just a sensor. Hooking a scan tool to it in order to see what the sensors are reading and if the module has the ability to move the doors is what we need to see.

The fact that it is blowing out of the defrost only is a safety default. The system obviously has an issue so the module forces the air to blow out of the defrost just to ensure your windshield does not fog up while driving. This would be a safety issue so it has to default to this position.

See the attached list. I highlighted the sensors that you need to monitor to make sure they are pretty even and reflecting the temp that you have the system set at. Also, the mode doors need to be checked and I circled those in red. Hopefully the tool has the ability to move your actuators. You will need to move them with the tool and then either listen for them to move or watch the actuator itself to see if it is moving the door when you command it to.

If all the sensors are reading properly and you can move the doors with the scan tool properly, then the control module is most likely the issue because you have proven out the inputs and outputs of the module. That just leaves the module.

Sounds good. Please keep me posted or if you have any other questions, I will be happy to assist.