Fresh air intake-- truck camping heat

[CAThrooper]

My son and I enjoy truck camping in Jake (2006 Expedition XLT) throughout the year. In the winter we head to the high desert and it gets fricken cold at night. I've rigged up a two speed USB computer fan in the passenger window driven by an Anker power supply to keep condensation down overnight and when combined with reflectex on the windows we stay fairly comfortable in Mar /Apr timeframe. I'd like to get my ventilation unit out of the window by permanently installing the vent fan in the HVAC of the truck to suck in fresh air when the truck is off, and I'd like to extend our time in the desert to Nov-Feb by warming the air being pulled from the outside by designing a heat exchanger that's heated by the exhaust of either a wood fire or charcoal brickets.

So, I bet this is a dumb question that clearly indicates my noobie status on these boards, but where does the fresh cabin air get sucked into the HVAC on our trucks?
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[TobyU]

I think it;s over on the pass side behind the glove box or on the inner fender area. A flap moves back and forth for max (recirc) or fresh air.
Most take the air in on the outside under the wipers on the cowl where there is a screened area.

 

[ExplorerTom]

Not vehicle specific, but check out www.expeditionportal.com for general camping and vehicle camping ideas.