How To Discharge AC System In Car

(Last Updated On: March 14, 2024)

When you’re looking to understand how to discharge an AC system, the initial aspect to contemplate is the impact of the refrigerant on the environment.

Your vehicle’s AC system uses refrigerant, typically R-134A (HFC-134a), which can contribute to ozone layer depletion and global warming. With this in mind, most countries, including the United States, deemed it illegal to discharge the refrigerant freely to the environment.

This article will guide you on the simple steps you need to take to correctly discharge your vehicle’s AC system. You will need a few tools to get you started and keep in mind the tips warnings mentioned afterward to avoid any mistakes.

Here is where that guide you on how to discharge AC system step by step
This article will guide you on how to take to correctly discharge your vehicle’s AC system.

Why do you have to discharge the AC system?

There are only three scenarios in which you would want to discharge the AC system; if you are running low on refrigerant, in case of a leak, and after replacing an air conditioning system component such as the condenser.

Your air conditioning system will start to malfunction the minute it runs low on the refrigerant. Low refrigerant levels mean enough heat is circulated between the vehicle and the AC system. The most common issue that will lead to decreased refrigerant levels is a leak in the AC hoses and vacuum lines.

Leaks in the air conditioning system are dangerous as they can cause compressor damages. Modern vehicles’ AC systems are designed to shut down when the refrigerant level has decreased below a stated point. This is done to avoid damaging the AC compressor, but sometimes systems aren’t accurate, and the compressors get damaged either way.

How to discharge ac system is the first thing you want to know before changing any components
It is essential to pay attention to the working condition of your air conditioning system since repairs.

It is essential to pay attention to the working condition of your air conditioning system since repairs, such as the replacement of the compressor, can be very expensive.

You will no need to discharge the air conditioning system unless you have the stated AC issues – leaks, low refrigerant levels, and a damaged AC compressor. These three issues are related to leaks leading to low refrigerant levels and eventual damage to the compressor.

Read more: What Kind of Refrigerant for My Car: All The Honest Overviews

The tools we need

The procedure difficulty for this process is easy, and you can easily do it by yourself if you have a bit of experience with your vehicle’s AC system. However, remember that you will need a few tools that can be expensive and hard to obtain. Feel free to loan them from your local mechanic or a friend. Here is the list of tools and requirements you will need for the process:

  1. EPA certification
  2. Refrigerant Purity Tool
  3. Vacuum line filters
  4. Air conditioning service/ recovery machine

You may be wondering, what is an EPA certification? The Environmental Protection Agency (EPA) certification in the United States is a certification, similar to others in various countries, that shows a technician or mechanic has enough skill and know-how on different laws that deal with HVAC (Heating, Ventilation, and Air Conditioning).

The EPA certification is vital for discharging your vehicle’s AC system since you are not legally permitted to do so without it. This is because of the dangerous aspects of the refrigerant to the environment. The severe consequences have prompted strict regulations limiting who can perform HVAC-related repairs on vehicles.  

The refrigerant purity tool is essential for testing the purity of the refrigerant in your system. It will help you know if your refrigerant is contaminated so that you can use the vacuum line filters to clean it up.

On the other hand, the air conditioning service machine is a system made of a vacuum pump, recovery machine, manifold gauges, and a recovery tank. The system is designed to be operated with slight adjustments, and anyone familiar with car repairs will easily get the hang of it.

Steps to discharge car AC system

Steps to discharge car AC system.
Seven steps to discharge car AC system.

Step 1: Determine the purity of the refrigerant

Begin the process using the refrigerant purity tool to test for refrigerant purity. This process needs to ensure you do not reuse a refrigerant that has gone bad due to contamination. Motor vehicle AC refrigerants can get contaminated through leaks that add environmental elements such as air and debris. They can also go faulty if there was improper AC servicing on your last visit to the mechanic. 

The AC service machine is a delicate tool that can be damaged with the slightest imperfections in the refrigerant. To prevent this, we use the refrigerant purity tool by connecting it to the high-pressure port of the AC system. 

You can easily locate the high-pressure and low-pressure ports on your vehicle by looking at the vehicle’s manual. Typically, the low-pressure side will be indicated by a negative sign/symbol, and the high-pressure side will have a positive sign/symbol. 

The purity tool will take out a tiny amount of the refrigerant through the high-pressure port and test it. Take a look at the indication to see if the refrigerant is pure or not. A pure refrigerant won’t warrant the use of the filters, but you will need the filters if the refrigerant has gone wrong.

Step 2: Connect the AC service machine

Proceed to take the AC service machine and connect it to your AC system. Start by removing the caps on the low-pressure port and the high-pressure port. Then, take the AC service machine red hose and connect it to your vehicle’s high-pressure port. Proceed to do the same for the blue AC service machine hose, which connects to the low-pressure port. Make the connection as tight as possible to prevent any leaks. 

Step 3: Add filters into the lines if the refrigerant is not pure

Take the filters and connect them to the vacuum lines if the refrigerant is impure. You should not allow impure refrigerants to be discharged by the AC service machine. Otherwise, proceed to discharge the system.

Step 4: Turn on the AC service machine

Power on the service machine once all the connections have been made. Take note of the readings on the gauges to see if there are any leaks. A lack of pressure readings will indicate a leak in the AC system, and you should fix the issue before proceeding. 

Once it’s on, the pump will suck in the refrigerant from the system by making a vacuum. The refrigerant will be sucked and directed into the recovery tank which is part of the machine. The recovery tank/reservoir tank will store the refrigerant till it is time to reuse it or dispose of it in case its impure. Never reuse an impure refrigerant since it will damage the AC system. 

Step 5: Make sure the system holds vacuums for at least 10 minutes

Let the machine run at least 10 minutes (it typically takes 10 to 30 minutes) till the pressure readings go to zero. A consistent zero reading on the gauges indicates that the vacuum has been held steadily, and refrigerant flow is not flowing through the system and service machine.

At this point, the system is fully discharged, and you can turn off the AC recovery machine if it doesn’t shut off automatically. 

Step 6: Program the recovery machine to dispense the car’s needed refrigerant

The Air conditioning service/recovery machines are modern and mainly automatic. All you will need to deal with the car’s refrigerant is to place a button that will either drain or recharge the system. The bad refrigerant should be sent for destruction to a destruction facility that uses destruction technologies. 

Step 7: Check the car AC system for standard functions

You are now done with the discharge process and can proceed to check the AC system for any malfunctions and much-needed repairs. Take a look at the hoses, vacuum lines, and any damages to the Ac components like the compressor and evaporator. 

Tips and warnings when discharging AC system

Do not dispense the refrigerant to the surrounding since this will be grounds for criminal charges. It is dangerous to the environment, too, since it contributes to ozone layer depletion and global warming. It is also hazardous for the human body when inhaled due to its toxic nature. Feel free to take the job to your local mechanic, EPA certified, if you are not.

You should avoid putting the refrigerant into the environment by ensuring the hoses are well connected during the discharge process. Any bad hoses and broken vacuum lines will also cause the refrigerant to leak out. Replace bad hoses and broken vacuum lines before discharging the system.

One last beneficial tip is to add small portions of refrigerants that come with fluorescent dyes into the system, which will help show leaks in the system when you use the service machine. Use a fluorescent detecting lamp to see where the dyed refrigerant is leaking from.


Discharging your car’s AC system is easy for anyone familiar with vehicle repairs. It will take you less than 30 minutes to get rid of the refrigerant but ensure you have an EPA certification to perform the process.

Read more: How To Vacuum Car AC System Without Pump

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