Great tip
@Sweeney and thanks for the tech explanation,
@Cary Winch dnk that on ACs. That would explain why the Dometic under the hatch closed on a hot day just cant cool below a certain point- the ambient air is just too warm?
Apologies to OP for OT, but a caution, to anyone back east visiting the SWUS:
Fwiw, I've camped a few times in very hot desert shoulder seasons over the years in the Sonoran desert (Anza Borrego, etc)
and agree you need to be VERY careful with heat. From SERE, JEST, and Wilderness First Aid they teach that ...
Once you get to the far end of hyperthermia you cant save yourself solo, as you cant make good decisions and for example
as BoyScout leaders we had to watch the little kids carefully- crabby/confusion etc- water up, cool down in the shade or else...
I once had to run the elderly Scoutmaster down the hill to hospital when he got heat stressed in his closed up tent...found him cold clammy and mumbling that progessed to hot dry...
Once you get really hot and stop sweating its heat stroke time...brain cooks. We couldnt wait for ambulance to drive uo the hill frim 45 min away. A close call the paramedics said.
Anything goes wrong and stuck out somewhere in 115 degree you are at risk, without a wingman.
I've parked in the shade, in a couple places around 110-115 including persuading Tucson area state park camp host to let me move the CI under trees vs park on hot asphalt in sun, as Sweeney mentioned - and this might help:
I've draped a wet towel over something to get the evaporate cooling on low moisture desert air, inside the cabin to cool it off to give the AC something cooler to work with vs the extra 10-15 degrees above ambient while sitting on concrete pavement/asphalt parked in the sun.
I believe the CI manual mentions being prepared to put a tarp or some other shade over the CI, and I have a Kelty and a couple poles to rig next time if no trees handy to tuck under.
Even so, I had to drink lots of ice water (dometic on freeze is great!) and drape wet bandanas on noggin and take a sit a couple times in the car with A/C max.
Pretty sure it got to 120 in the area.
AZ heat can be wicked in summer.
Better trip planning would be in a nice cool WI honkey tonk with on tap; "Hamm's the beer refreshing Hamms..."