2011 Honda Pilot Middle Vents Weak Air

Okay, does it blow hot or cold if you select floor or defrost? Then just doesn't blow out the vents or is it that you can select any position and cannot get hot or cold air? If it's that you can't select floor-dash-defrost, that is the mode actuator. That is the image and red underlined item. To get to it you need to pull the trim off the dash and the glove box. For that you remove the end cap and then the trim using plastic trim tools. Then you unbolt the glove box and push in the retainer clips, then the box comes out. Behind it is the duct that has to be removed to get to the actuator. You remove the screws and the connector, and the actuator comes out.
Now if it is that you get air out of the floor-dash-defrost vents but cannot select hot or cold temperatures, that would be the blend actuators (purple lines) If you only have a single control for hot-cold then the actuator is the one to the left in the first pic and you access it by going under the driver's side dash and removing the duct as shown, then the actuator is behind it. If it is the dual zone system the passenger actuator is reached by removing the dash trim as above, then the actuator is mounted to the HVAC case. Reverse the processes to install replacements.