In case there is any doubt.
Page 44 of the manual.
"Avoid leaving your phone in your car in high temperatures."
Now just because the AC is on and the ambient temperature is comfortable the phone itself is in direct sunlight when mounted on the windshield or dash. Your best bet if you want to use navigation in the car is to get a stalk mount or face mount on the dash. At least then the unit would be out of direct sunlight and can even have cool air directed at it from one of the cars dash vents.