Park the car on a level surface and turn off the engine
Set the A/C to maximum cooling and fan speed
Open the hood and locate the A/C low-pressure service port
Check the refrigerant pressure with an A/C manifold gauge set or low-side gauge
Compare the reading to the vehicle manufacturer’s specified pressure range
Inspect the sight glass, if equipped, for bubbles or clear flow
Check for signs of leaks around hoses, fittings, compressor, and condenser
Verify compressor clutch engagement when the A/C is turned on
Check vent temperature inside the cabin
Have the system checked by a qualified technician if the pressure is low or uncertain