I didn't have an automobile with Airconditioning until around 1990. We manually rolled down the windows
We installed central Airconditioning in our house in 1991 (we had a 48" attic fan and a window airconditionaire before that... with open windows)
I didn't have a truck with airconditioning until November 2002,
Our 1970 Chev 21034 came with two window cranks and big vent doors near the floor.
We had a truck camper with no airconditioning from 1970 until 2003. From 1970 until the mid 1990's Janet and the kids traveled in the TC... we had a battery powered intercom and they operated the windows and escape hatch.
You can bet the the windows were open and the hatch was cracked open ... it was hot outside... and would've been much hotter in the camper without the moving air.
No one had to ask or rationalize... we were smart enough to let air in and heat out by opening windows and vents.
We knew that moving air is always cooler that "dead" air.
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We keep our 2003 camper cooler:
We leave the wheel well door under the fridge open. I installed a 24" x 24" furnace filter over the opening in the wheelwell side (stops mosquitos and dirt) Rain can't get in through the wheelwell either.
And... we have a model 6150 Fantastic Fan in the camper bathroom that opens and closes automatically... rain or temperature sensors control it.
Our little system takes care of itself... on the highway, in camp, or at home.... and has for 10 years.
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By all means... open the windows... it has always worked, even on stage coaches.
Sleepy :R