I charged my air conditioner with one, 12 ounce, can of R134a. I also added one, 4 ounce, can of oil charge(containing 2 ounces of R134a and 2 ounces of polyol ester lubricant) to the low side. The air conditioner now works great. The low pressure side is now cold with condensation. Before it was just cool with no condensation. You can buy, what looks like a tire pressure gauge for auto air conditioning, to check the low pressure side and find out if the system is under charged.