Low pressure readings, or the absence of pressure at all, will indicate that there is usually a leak somewhere that must be located and repaired before adding more refrigerant, which thanks to the Clean Air Act enacted by the U.S. federal government, no longer contains chlorofluorocarbons that we now know to be extremely harmful to the atmosphere’s delicate ozone layer. While it is completely normal, and even necessary, for a car’s air conditioner to lose some of its refrigerant, larger leaks will cause a noticeable loss of performance. If diagnostic tests do reveal either low or no pressure coming from the system, a technician must scan it to locate the problem area and ascertain if the leak is liquid or gas refrigerant and which components must be replaced.