No, it's spot on. I've been working on cars for decades. From a practical stand point (from the consumers view) those conditions and temps are a good indicator that the AC system will be up to the task of providing a quick cool down, and be able to adequately maintain that comfort, especially when you are sitting still in 90+F heat!
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You're over-simplifying it. Yes, measuring temperature with a 4- 6" probe sticking down into a vent is a good place to measure the coolest air being produced, and the fan needs to be running fast enough to get a good volume-rate of cold air flowing through the vents. But the thing you're NOT taking into consideration is HOW LONG it takes many of these new 5th-generation ("DT") Rams to begin to produce the necessary cold temperatures down inside the vents. The problem with many of these 5th-gen Rams is that the AC system is literally fighting itself, wasting much of the energy it takes to produce the cold air, by having to overcome the heat of the full flow of engine coolant being constantly circulated through the heater core in the cab, and/or the blend doors being poorly programmed. So it takes them forever to achieve cooler temperatures, if they ever do achieve cool vent temperatures, because the AC system is, apparently, also cooling down the heater core with full flow of coolant passing through it at all times.
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When, on a 90 °F day with 50% relative humidity, my 15-year-old Prius
and my wife's 6-year-old Mini can both produce 45 °F air within 40-60 seconds, and a 2019 Ram that cost literally 2.5X what the Prius cost and 2X what the Mini cost, can barely produce 52 °F air in the vent within FIVE MINUTES, then there is absolutely, positively, NO QUESTION that there is something wrong with the Ram's AC system.
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And don't confuse the time it takes to
begin producing cold air down in the vent with the time it takes to cool down the entire cab of a Ram 1500 Crew Cab - of course it takes longer to cool a huge cab, especially a dark-colored vehicle with a huge pano roof. The point is, if the compressor, condenser and evaporator are all working properly and as designed,
EVERY ONE OF THEM SHOULD BE ABLE TO BEGIN PRODUCING EQUALLY COLD AIR (45 °F OR COOLER) DOWN IN THE VENTS WITHIN 60 SECONDS OF STARTUP.