Thermometer Trick for Vents

https://reidomue525.vantagequill.com/posts/comfort-experts-explains-capacitor-and-contactor-failures-in-north-fort-worth-ac-repair

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