A question we hear often is, “How do I know how much refrigerant to add to my car’s A/C?”
Stated simply, it depends.
(1) It depends on the car. Most cars will hold between 28 and 32 ounces of refrigerant (or about 2-3 12oz cans), however larger vehicles and those with rear A/C will likely hold more. Check your vehicle manual for proper system capacities. Remember that you will most likely have some refrigerant left in your system so you will not be required to install the full capacity of refrigerant each time. Too much and too little refrigerant in the system both will make the system not work properly. Consider using a manifold gauge to measure how much psi’s are in the system. The gauge will help identify when your vehicle’s refrigerant level is adequately pressurized. Too much refrigerant in a system does not lead to cooler air. In fact, it may flood your evaporator and cause warm air. The low-pressure gauge should read between 25 and 40 psi (pounds per square inch). The high pressure gauge should read between 225 and 250 psi. You can also use a thermometer on your dashboard vents to test the temperature of the air coming out during a recharge. When everything is working properly your a/c system on max cool should be blowing out air that is around 38-48 degrees F.
(2) It depends on why your system is blowing warm. Most times an A/C system isn’t cooling properly it’s due to a small refrigerant leak. By its very definition, small leak leaks slowly, so there’s really no way to know how long it’s been leaking, or how much refrigerant remains in the system. The best option would be to remove and recover all the refrigerant that remains in the system, repair the leak, and charge it with the precise amount that your OEM recommends. Another solution is Kwik Seal Leak Sealant FJC Part #9165. This advanced formula stops small leaks in metal and rubber components. However, if your system is blowing warm due to a worn out compressor or problems with the electrical system, these options will not help rectify the situation.
An A/C system has a variety of components, hoses and fittings that circulate and pressurize refrigerant. Understanding the system and the steps for a refrigerant re-charge will keep your system from being over– or under-pressurized.