One of my favorite tools for diagnosing A/C issues: anemometer

One of my favorite tools for diagnosing A/C issues is the HT-81, a tool that is inexpensive and can be purchased from a variety of sources.  I do not use the HT-81 for temperature when doing diagnostics. I use it for air flow only. I don’t use an infrared thermometer for measuring air temperature from the vents as they can register an incorrect reading due to emissivity issues.  Taking vent temperatures with infrared can be misleading because you are reading the temperature of a solid surface, not necessarily the air coming out of the vent. If I take the wrong temperature, I will make a diagnostic mistake.  I prefer a digital thermometer in the vents as it updates the display faster and I can leave it in place for the entire diagnostic and repair process. The HT-81 does measure temperature and we do use it when we are talking with a customer. We let the customer see speed and temperature before and after the repair. It is a great way to show the need for cabin air filter.