Thermometer Trick for Vents
https://manuelgrwb589.wpsuo.com/a-comfort-experts-checklist-for-ac-tune-ups-and-fewer-north-fort-worth-ac-repairs
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