5.9L Diesel. My re-cir vent broke and I have cold air coming into the cab. I have taken off the blower motor and removed the door so I have more air flow from the blower which is nice, but I would like to cover the exterior vent for the winter to stop the cold air. I was told to cover this opening, I would need to remove the cowl covering the wipers/wiper motor. I have taking it lose and looked under it and I don't see anything that looks like a vent to enter air into the cab.

Where is this located?