Connecting and Disconnecting Gages
CAUTION: Never remove a gage line from its adapter when the line is connected to the A/C system. To disconnect a line, always remove the line adapter from the service fitting. Do not remove a charging hose from the gage set while the hose is attached to the low-side service fitting. Doing so will cause the system to discharge completely because the Schrader-type valve on the fitting is depressed. This discharge may cause personal injury due to escaping Refrigerant-12.