Thermometer Trick for Vents

https://johnathanmczl781.talesignal.com/posts/electrical-panel-problems-behind-ac-repair-in-north-fort-worth-and-where-comfort-experts-fits-in

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