So in my 1990 F150 that was non ac, I added ac a while back. One of the curious parts I chose not to mess with was the dash controls because the donor truck had the ugliest destroyed hvac panels ever, so I put a toggle switch to send power to the low pressure switch on the drier to give power to the ac the same way normal ac and max ac do. I just put the slider to vent and press the button and ac is on. Works great. After my debacle with some of my ac components on my 350 I started thinking about the recirculation door and what is it doing on this truck and it turns out when the truck is off the recirculation door is "recirculating" but on legit any setting while running it opens to "vent" outdoor air. I'm guessing my only option is to sit the little vacuum doohickey backwards so it does nothing and manually leave the door on recirculation mode for summer when you'd never want outside air or rig up some sort of choke cable to the door? It's not like my settings do anything but that seems wrong as my non ac hvac blower housing had a recirculation door / vacuum module in the same spot.. I can't figure out why if it does nothing?