Certified RV technician
I get questions all the time regarding RV temperatures. People ask about their heating and air conditioning, their wheel and brake temperatures, refrigerator temperatures, oven temperatures . . . you get the point.
A quick and easy way to see various temperatures is to use an infrared thermometer. These battery-powered units fit easily in your RV toolbox or drawer, and have a laser to see where to aim it.
IR thermometers don’t work on air temperature, just solid surfaces; but it’s still pretty easy to find a surface to read that’s reflective of the temperature you want to know. For instance, it is often necessary to measure the difference between the air going into an RV air conditioner (return air) and the discharge or register air. Simply measure the temperature of the return air and the closest register grill to the A/C unit and you’ll have it!