Thermometer Trick for Vents

https://manuelwrlp832.quillnesty.com/posts/ac-repair-in-north-fort-worth-and-plumbing-help-under-one-roof-at-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