The vent temp tells you

The vent temp tells you where the AC system is failing. Customer says AC isn't cold enough. You check pressures, they look fine. Here's where most techs stop. And here's where you should be starting. Grab an infrared thermometer or a temperature probe. Measure the air temperature at the center vent. Then measure the ambient air temperature at the evaporator inlet. Then you wanna subtract the two. That's your delta T, your temperature split. A properly operating AC system should drop that temperature by 35 to 50 degrees Fahrenheit across the evaporator. The split is within range, but the customer's still hot. You're looking at blend doors, duct leaks, or air flow volume. The AC is working, the air isn't getting there. Split is too low, under 20 degrees. The system isn't transferring heat efficiently. That could be low refrigerant, a weak compressor, restricted evaporator. Your gauges and your superheat give you the next step. The vent temp is not the final answer, but it tells you immediately where the problem is inside of the AC system or somewhere between the system and the customer. Most techs skip this step and go straight to the gauges. The ones who measure first waste half as much time than the ones who don't. Make sure you guys join me for my air conditioning class. Charge it right, fix it fast, here at Master Automotive Training. I'll see you in the next one.