Thermometer Trick for Vents

https://lukaseolt009.swiftnestly.com/posts/comfort-experts-ac-repair-north-fort-worth-homeowners-can-count-on-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