A reading on the low side of 21 PSI at 1,500 RPM translates to an evaporator temperature (coincidently) of about 21°F, which will cause the evaporator to freeze-up and block airflow through the vents under certain conditions. It's also an indication that the system is undercharged. The Schrader val...

I am trying to workout my wife's A/C problem. 2007 Mazda MX-5 (Miata) GT. Today her A/C works great, but when it is hot outside it does not get cool at all vents are warm. I hooked up a manifold and went through the pressure test as per the Mazda manual. Here are the numbers: Engine warm @ 1500RPM,...

I am trying to workout my wife's A/C problem. 2007 Mazda MX-5 (Miata) GT. Today her A/C works great, but when it is hot outside it does not get cool at all vents are warm. I am not sure if a switch or sensor is to blame, what do you think? I hooked up a manifold and went through the pressure test as...