Thermometer Trick for Vents

https://kameronxzbm553.lakeviewbrief.com/posts/what-you-can-fix-yourself-and-when-north-fort-worth-ac-repair-needs-comfort-experts

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