A thermochromic clip provides a visual indication of the temperature of the air flowing through an air vent as refrigerant is introduced into an air conditioning system. The thermochromic clip including an elongate body having an outer facing surface; a fastening member on the elongate body. The fastening member being sized and configured for selective attachment to the air vent. At least the outer facing surface coated with a thermochromic material. The thermochromic material of the outer facing surface being structured and disposed for changing from a first color state to a second color state in response to a change in temperature that places the thermochromic material at a temperature equal to or below a predetermined temperature value.