Thermometer Trick for Vents

https://paxtonumsa058.northstarcolumn.com/posts/short-cycling-ac-repair-explained-for-north-fort-worth-homes-by-the-comfort-experts-team

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