I've known of an issue on my 2014 300 since I've had it. The defrost vents do not close. I've dealt with it and just put some faux leather across the vents that I can pull off when defrost is needed. Well, now the HVAC system wont change temperature on either side unless I have recirculation on. I know there are 4 actuators; 2 behind the glove box and two behind the dash next to the steering column. Which ones could be the culprit. I'm an aviation mech so tools and skills arent an issue. Just wanting to know which ones could be causing the issue.