How to Add Refrigerant to a Car Air Conditioner?

[VanFinn]

There are two methods for adding refrigerant to a car air conditioner. One is the high-pressure side charging, which is suitable for charging after leak detection and vacuuming. Note that this method cannot be used with the compressor running, and the engine must be off, with the refrigerant canister required to be inverted. The other method is low-pressure side charging, where gas is added. This method is characterized by a slower charging speed and is typically used for replenishing refrigerant. Steps for high-pressure side refrigerant charging: 1. After the system is vacuumed, close the high and low-pressure manual valves on the manifold pressure gauge. 2. Connect one end of the middle hose to the refrigerant canister injection valve. Open the refrigerant canister valve, then loosen the nut at one end of the manifold pressure gauge hose to allow gas to escape for a few minutes, then tighten the nut. 3. Fully open the high-pressure side manual valve and invert the refrigerant canister. 4. Inject the specified amount of liquid refrigerant from the high-pressure side. Close the refrigerant canister injection valve and the high-pressure manual valve on the manifold pressure gauge, then remove the gauge. When charging refrigerant from the high-pressure side, the engine must be off (compressor not running), and do not open the low-pressure manual valve on the manifold pressure gauge to prevent hydraulic shock. Steps for low-pressure side refrigerant charging: 1. First, connect the manifold pressure gauge to the compressor and refrigerant canister. 2. Open the refrigerant canister and loosen the nut on the manifold pressure gauge until you hear the sound of refrigerant vapor flowing, then tighten the nut to expel air from the injection hose. 3. Open the low-pressure manual valve to allow refrigerant to enter the refrigeration system. When the system pressure reaches 0.4MPa, close the low-pressure manual valve. 4. Start the engine, turn on the air conditioner switch, and set the blower switch and temperature control switch to maximum. 5. Open the manual valve on the manifold pressure gauge to allow refrigerant to continue entering the refrigeration system until the specified amount is reached.

[BradyDella]

I've done this job hundreds of times, and the steps are actually quite systematic. First, you need to prepare a set of refrigerant charging tools, the most crucial being a manifold gauge set. Locate the low-pressure pipe connection—usually the thinner pipe is the low-pressure one. After connecting the gauges, evacuate the pipeline for about 20 minutes to remove all air and moisture inside. Then, turn off the vacuum pump and connect the refrigerant can. With the engine running, set the AC to maximum and turn on recirculation mode. Slowly open the valve to add refrigerant, keeping a close eye on the pressure gauge needle. In summer, the low-pressure side should be around 25 to 40 psi, while in winter it should be slightly lower. After filling, check for leaks at the connections by applying soapy water and looking for bubbles. It's best to wear goggles and gloves throughout the process—last time a rookie got frostbite for not wearing gloves.

[VonSadie]

Last time I tried adding it myself, the key was finding the correct port. The low-pressure port in the engine compartment is a silver metal fitting about the thickness of a finger, with an 'L' on its cap. Before adding refrigerant, you need to get the AC system running first - I always start the car and turn the AC to max fan speed for two minutes. I bought a simple kit online for 40 yuan that even included two cans of refrigerant. When adding, you have to turn the can upside down to let the liquid flow in, but twist it very slowly bit by bit - otherwise when the pressure gauge needle suddenly spikes, it'll scare you to death. Stop when you feel the cold air is sufficiently cool, and be careful not to overfill. But honestly, if you're not confident, it's much safer to go to an auto repair shop - their professional vacuum equipment works way better than doing it yourself.

[SanKai]

When adding refrigerant to the air conditioning system, pay attention to the vehicle's production year. Cars manufactured after 2009 mostly use R134a refrigerant, while older vehicles may use R12, which is now obsolete and should not be added randomly. You can buy a complete toolkit for around 200 yuan at auto parts markets, but the key is to check the sealing rings for cracks before use. Always operate in a well-ventilated area—I've seen cases where people got poisoned and hospitalized from doing this in garages. The process is simple: connect the gauge and vacuum for at least 15 minutes, slowly open the can valve to inject refrigerant, and finally check the pressure before disconnecting. The most common mistake beginners make is forgetting to turn on the AC compressor, which prevents the refrigerant from entering the circulation system.