Adding refrigerant to a car's air conditioning refrigerant system is a quick easy way to make your car blow cold air again right? Well although this practice is very common - people are many times adding freon without any idea of what the pressure readings are and this can be dangerous. And many times the problem won't even be low refrigerant, but if ac gauges are not used how is one you know? Blindly putting 134A into a cars air conditioning system without knowing the capacity, how much is in the system already or even knowing what the low and high side readings are, is not recommended. Using an inexpensive single hose, no gauge A/C charging kit like the ones sold at parts stores can cause damage to the cars AC system.