Patent ID: 8825429

Claim:
A refrigerant recovery machine for use with a vehicle's cooling system, comprising: a refrigerant container containing a refrigerant for use with the vehicle's cooling system; a scale having a first side and a second side, wherein the first side is coupled to the refrigerant container to measure a weight of the refrigerant container in order to determine an amount of refrigerant in the refrigerant container, wherein the measured weight is a reference point to zero out the scale; a magnet coupled to the second side and configured to directly couple to a precalibrated weight having a first weight, wherein the precalibrated weight is located below a plane containing the scale; a pump configured to move the refrigerant to and from the vehicle's cooling system; an input device configured to receive an input selection to perform a scale calibration; a display configured to display information including a prompt to perform the scale calibration; and a controller that controls the scale, the pump and the display, wherein the controller is previously programmed with the first weight and wherein the controller is configured to determine if the scale is calibrated within a predetermined tolerance without having to remove the refrigerant container.