Thermometer Trick for Vents
https://stephenxpta941.wordcanopy.com/posts/indoor-air-quality-problems-that-point-to-ac-repair-in-north-fort-worth-and-how-comfort-experts-can-help-2
Thermometer Trick for Vents Quick tip from our house: put a cheap kitchen thermometer in a supply vent after the AC runs 15 minutes, then check the air at the return. We see about an 18 degree drop when things are healthy