My wife and I have a 2015 Winnebago Forza 34T diesel pusher. We are experiencing a problem with the dash heat controls. I believe I have determined the problem or at least part of the problem. There is a vacuum controlled "modulator" that moves the door or flap to determine if air goes to the dash or floor or a mixture. This modulator (I believe that is the correct terminology) is vacuum operated and has a tear in the rubber membrane. Easy to replace but difficult to find the part. Looking for assistance finding the part.