How to Empty a Car AC System (DIY Guide)

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Car air condition repair service with the AC vacuum pump machine hooked up

Taking care of your car is the best way to ensure it lasts for a long time and that it works properly. One of the most important, but most often forgotten, things that need maintenance is the air conditioning (AC) system of a car. There are multiple different ways to clean it out, and multiple different products you can use to do so.

The easiest way to empty a car AC system is with a vacuum pump. It helps to flush out any air and moisture in the air conditioning. It also helps to prepare the AC system for any extra maintenance.

The following article is a thorough guide on how to empty a car AC system, with and without a vacuum pump. It will also discuss the best car cleaning equipment, as well as the various reasons why you should keep your car’s AC system clean. Finally, the article will go over a few other common car AC issues and their fixes.

How To Empty A Car AC System With A Pump

The basic steps to empty a car AC system with a pump include:

  • Get the right equipment
  • Hook up the vacuum pump
  • Flush out the AC system

Once the basics are completed, you can start on any other maintenance that’s needed.

What You Need and What to Do

The first step to emptying a car AC system with a pump is to get the right equipment. The main piece of equipment you will need is, of course, a vacuum pump. But the best pumps for emptying car AC units will be discussed later in the article. In addition to a car pump, you will need:

  • Protective goggles and gloves
  • Manifold gauges, to monitor your car’s cooling system
  • AC Recovery unit, which moves the refrigerant to the recovery tank
  • Recovery Tank

Gloves and goggles aren’t required, but they are highly recommended to safely work on your car’s AC unit. Make sure to prepare the recovery tank by opening its valves and releasing nitrogen into the tank. Once you have all of the equipment, the next step is to hook up the vacuum pump to the AC system.

To hook up the vacuum pump, attach it to the recovery tank’s blue valve. Make sure the other valves on the recovery tank are closed as you do this step. Next, turn on the vacuum pump as you open the blue valve. Leaving it on for about an hour will remove all of the air and moisture from the tank.

When an hour has passed, connect the manifold gauges to your car’s AC recovery unit. Slowly open the blue valve on the recovery tank and open the blue liquid valve on the manifold gauges. This will remove any liquid that’s in the AC system. Once that’s done, open the red valve on the manifold gauges to finish flushing out the system.

Let the flushing process run until the manifold gauge reaches zero, which usually takes about 30 to 45 minutes. Once you’re done, disconnect the recovery tank and manifold gauges and replace everything in your car. Make sure all valves are also closed tightly to avoid any leaks. 

MASTERCOOL – 50# Recovery Tank for 69100 (63010)

MASTERCOOL - 50# Recovery Tank for 69100 (63010)
AC Recovery Tank

Orion Motor Tech 3-Way Car AC Manifold Gauge Set for R134a R12 R502 Refrigerant with 5ft. Hoses Couplers & Adapter, Puncturing & Self Sealing Can Tap Freon Charge Kit

Orion Motor Tech AC Gauges, AC Manifold Gauge Set for R134a R12 R502 Refrigerant, 3 Way Car AC Gauge Set with 5FT Hoses Couplers & Adapter, Puncturing & Self Sealing Can Tap Freon Charge Kit
A/C Manifold Gauge Set

How To Empty A Car AC System Without A Pump

You can also empty a car AC system without a vacuum pump. The steps to do so include:

  • Depress the system’s access valves
  • Charge the low side valve
  • Disconnect pressure from the high side valve
  • Repeat as needed and charge with refrigerant 

This process is less complicated but still effective.

AC lines with fittings
A/C refrigerant pressure lines

What You Need and What to Do

Emptying a car’s AC system without a pump requires less equipment. All you need is:

  • Protective goggles/gloves
  • A couple of access valves
  • Refrigerant

First, connect the access valves to the high and low sides of your AC system compressor. Once you have connected them, close the valve on the high side and specify compressor pressure on the low side. This will cause pressure to build up to the point where the high side valve closes, and the compressor will shut down.

The next step is to charge the low side valve of the AC system. Adjusting it until it reaches 14 psi will generate enough friction. Letting the friction run for a few minutes will allow the pressure on both the “Low” and “High” sides to reach equilibrium.  

Once the low and high sides reach equilibrium, or close to it, disconnect the pressure from the high side valve. To do this, turn the compressor behind the service valve and push it against the high valve.

Close the valve on the high side and the compressor until the low side valve reaches operating pressure. Repeat these steps for the next three minutes or so to fully flush out the AC system.

After three minutes have passed, pump refrigerant into the AC system. This will recharge the system and make sure it functions properly after being flushed out. You can find out how much refrigerant your vehicle’s AC system needs via the owner’s manual. Make sure you turn off the compressor once you’re done.

Refilling the car's air condition AC through the recharge valve port close up
A/C recharge valve

Best Car AC Vacuum Pumps

Even though you can empty a car AC system without a vacuum pump, doing so with one is the best way. But it’s also important to purchase a high-quality vacuum pump, to ensure it lasts a long time and will continue to do an effective job.

There are multiple things to consider when selecting a vacuum pump, including:

  • Price
  • How long it will last
  • How much power it has
  • Other features

The next section of the article will briefly go over five highly rated vacuum pumps, analyzing each aspect mentioned above.

Mastercool 90066-B 6 CFM Single Stage Vacuum Pump

MASTERCOOL 6 CFM Single Stage Air Vacuum Pump 90066-B

The first vacuum pump on this list is incredibly efficient, yet still powerful. It also comes with multiple useful features to make emptying out your car’s AC system easy, all for a great price.

The first vacuum pump on this list is the Mastercool 90066-B 6 CFM Single Stage Vacuum Pump. It’s a single-stage vacuum pump that can get up to an incredibly powerful 80-micron. This makes it an incredibly powerful and efficient vacuum pump and will empty your car’s AC system in no time.

Some other features of this vacuum pump include:

  • Motor with an on/off rocker switch
  • Can monitor oil quality and level
  • Can easily access oil drain valve, in case oil got stuck in the car’s AC system

If its power and features aren’t enough, it’s also one of the least expensive vacuum pumps on this list. At only $149, it’s a steal for how efficiently it will empty your AC system and will last for years without losing any power.

JB Industries DV-6E Eliminator 6 CFM Vacuum Pump

JB Industries DV-6E Eliminator 6 CFM Vacuum Pump

This vacuum pump is best for tough AC jobs, such as a car AC system that has never been emptied before. It’s very heavy duty and is able to withstand even the largest or most clogged AC systems.

The JB Industries DV-6E Eliminator 6 CFM Vacuum Pump is the most heavy-duty vacuum pump on this list. It has a 1725 RPM (revolutions per minute) capacitor-start motor and thermal overload protection, making it ideal for larger AC systems or systems that have never received maintenance before.

A few other features of this vacuum pump include:

  • Easy to transport, despite being heavy duty
  • A gauge is included to monitor oil quality and level
  • Durable and reliable

But being so heavy duty does come with one main drawback; the price. This vacuum pump is the most expensive one on this list, going for about $400. Despite the price, it’s made of very durable material and will last for years, completing every job no matter how difficult it may be.

FJC 6912 Vacuum Pump 5.0 CFM

FJC 6912 Vacuum Pump 5.0 Cfm

This vacuum pump gives the most value for its price. It’s very efficient and is considered the best vacuum pump for someone that wants to empty a car’s AC system themselves. It’s fairly easy to figure out and use, yet still able to fully empty an AC system.

The FJC 6912 Vacuum Pump 5.0 CFM is the best vacuum pump on this list for DIYers. It’s a single-stage pump that can get up to 75 microns and 5 CFM (cubic feet per minute), so it’s very efficient yet still powerful.

A few other features of this ideal DIY pump include:

  • A twelve-ounce oil capacity
  • A no-slip grip handle
  • A motor that has ⅓ HP and 1725 RPM

It’s also one of the less expensive pumps on this list, at only $170. This makes it a perfect first vacuum pump to buy if you’re just learning how to take care of a car’s AC system, or if you want to continue maintaining the system yourself.

HFS R Vacuum Pump Double Stage

HFS R Vacuum Pump Double Stage 12CFM - 340 L min - 110V-60HZ - Inlet Port - .25in. and 3-8in. SAE - Ultimate Vacuum - 2Pa or 15 microns - Power 1HP

This vacuum pump is the most diverse one on this list. It’s available as a double and single stage and in multiple different CFMs. The double-stage version is the most popular, but this vacuum pump has a model to fit whatever your AC system needs.

The HFS R Vacuum Pump Double Stage is the most versatile vacuum pump on this list. The double-stage version is the most popular and the most powerful, but the brand has multiple different models to fit what your AC system needs.

A few different models of this vacuum pump include:

  • Single stage
  • CFM 3
  • CFM 6
  • CFM 12

Features

In addition to different models, this vacuum pump also has different features. A few of them include:

  • Power 1 HP pump
  • 2 Pa pressure with 15 microns
  • 1/4″ port size for inlet and 3/8″ for SAE

The price of these models ranges slightly, but they usually cost around $250. This vacuum pump will last for years, and you can get the model that will perfectly fit your car’s AC system needs.

Vivohome Dual Stage Rotary Vane HVAC Air Vacuum Pump

VIVOHOME 110V .5 HP 5 CFM Dual Stage Rotary Vane HVAC Air Vacuum Pump with Oil Bottle ETL Listed

The final vacuum pump on this list is also a great fit for DIYers. In addition to emptying it out, the pump allows the user to self-diagnose AC systems and find out if there are any other issues. It’s very efficient and powerful, while still being easy to use.

The Vivohome Dual Stage Rotary Vane HVAC Air Vacuum Pump is a great vacuum pump for emptying out a car’s AC system yourself. It efficiently removes any moisture or dust that is trapped in the system and immediately refills the system with refrigerant afterward.

It also has a feature that allows users to self-diagnose AC systems to see if there are any other issues that require extra maintenance.

Some other features of this vacuum pump include:

  • Works for automotive AC and HVAC 
  • High vacuum pull from a compact pump
  • Easy to handle and transport

It’s also one of the least expensive vacuum pumps on this list, at only $120. It will last for years and still be able to perform effectively and efficiently.

Why You Should Clean Out Your Car’s AC System

The main reasons you should clean out your AC system are to keep it functioning properly and to help your car last longer. It’s also important to keep the system clean to ensure you don’t inhale anything harmful.

Car AC systems can get clogged with multiple different substances, including:

  • Fur
  • Dust
  • Hair
  • Pollen
  • Small debris, such as pebbles

When there is too much of this substance in the AC system, it makes it have to work even harder to pump air out. This can put a severe strain on the system, and cause it to fail prematurely. A malfunctioning AC system can also deplete the car’s value overall, so it’s very important to keep it clean and maintained.

Keeping the car’s AC system also decreases how hard the engine has to work and your fuel consumption. This will help lower your car bill each month and save you a significant amount of money in the long run.

Fixing a car AC system that has not been taken care of is very expensive, with costs ranging from $1,000 to $4,000 dollars. If you regularly empty it out and maintain it, you will save lots of time and money.

Mechanic inspecting the air condition AC compressor with a manifold gauge kit to test if it's functioning properly

What Happens If A Car’s AC System Is Neglected?

If a car’s AC system is not emptied and maintained frequently, then the various parts of it could start wearing down and affect the system’s performance. This will cause multiple issues to occur, making the problem more difficult to solve.

The AC system of a car has multiple different parts, all of which perform important functions to keep things running smoothly. The parts of a car’s AC system include:

  • Compressor
  • Evaporator
  • Filters
  • Condenser
  • Receiver Dryer/Accumulator
  • Orifice Tube/Expansion Valve

Air passes through each of these parts until it reaches the vents and flows into the car. But if they aren’t maintained properly, multiple issues can occur. The most common thing that happens when a car’s AC system is neglected is the cabin temperature gets very hot.

A clogged AC system’s compressor won’t work right and the refrigerant can’t be regulated properly. This causes the car to be unevenly cooled and the cabin temperature will be abnormally high. Other common issues that will arise if an AC system isn’t cared for are loud noises from the compressor and a foul odor in the car.

Loud noises from the compressor indicate that it’s working twice as hard, and the parts will wear down faster. It’s recommended to empty the AC system or get it checked out as soon as possible if these noises start occurring.

Furthermore, a foul odor in the car can indicate a build-up of mold or other substances in the system. If you start smelling rotten eggs or wet socks in your car, then it’s highly recommended to have a professional check it out since emptying it likely won’t get rid of the problem.

Bad car smell coming from the vents due to the AC refrigerant air conditioning system being broken
Foul odors can be emitted from the interior vents

Other Common Car AC Issues

If your car AC still isn’t functioning properly after emptying it, then there might be another issue that needs to be taken care of. Fortunately, you can also fix the majority of these issues by yourself.

Emptying out a car’s AC system will take care of most issues. But there are still a few problems that may come up that require more maintenance and work. Fortunately, each of the problems explained below has easy fixes that you can perform yourself.

Broken or Blocked Condenser

The condenser is a coiled piece of equipment, and debris can easily get stuck on the curves and clog it up. If it gets too clogged, then it could break. To fix this issue, clear out the debris by hand.

The condenser is located at the front of your vehicle and is where the air starts getting cooled. It is a very coiled piece of equipment, with coils stacked vertically on top of each other. Because of its design, debris tends to get easily stuck on the curves. When the condenser is blocked, air can’t get through and won’t cool down.

If the condenser gets too clogged up, then it could break and cause even bigger issues. If it does break, then you should have a professional replace it. To prevent this from happening, all you have to do is clear out the debris by hand. Putting on some gloves and emptying the condenser into a trash can before putting it back will return it to full functionality.

AC condenser clogged up
A/C condenser clogged up

Cabin Air Filter is Clogged

The cabin air filter catches air that comes through the AC system and goes through the vents. It helps to catch any debris that might be in the air. If it gets clogged, then the air won’t filter properly. To fix this, change out your cabin filter.

The cabin air filter is a small screen that catches any debris that might be in the air, from dust to pollen and even small pebbles. Over time, the filter gets clogged with debris and won’t filter the air properly. This will cause not enough air to pass through, and your car won’t be cooled effectively.

Fortunately, there is a very simple solution to this; replace your air filter. You can get one at any auto parts store, change out the clogged one for a fresh one, and you are good to go.

Comparing a dirty and brand new cabin air filter with the glove compartment storage open
Comparison of an old vs new cabin air filter

Mold and Bacteria Build Up

Mold and bacteria can build up in your AC system due to moisture from the outside air. If too much builds up, then it could cause you to inhale harmful substances. All you have to do is use a cleaning agent and wipe down your air vents.  

Moisture from the outside can get into your car’s AC system from the outside, especially if you park outdoors. If enough moisture gets in, it can cause mold and bacteria to build up in the system, primarily in the vents. If the build-up becomes too excessive, then you could start inhaling harmful substances against your will, which can negatively affect your health.

To take care of the build, get a cleaning agent and a rag and wipe down your air vents. You should do this often if you live in humid conditions or somewhere it rains a lot, as this increases the likelihood of mold buildup.

Close up of mold in an air conditioning system of a car which is bad for inhaling and cause of respiratory pneumonia
Close-up of mold accumulating on the AC system components

Overheating Engine

An overheating engine can cause warm air to blow into your car. Since the AC system and car engine are so close together, heat can transfer fairly easily. To fix this, figure out what is causing your engine to overheat as soon as possible.

The engine and the car’s AC system are very close together. So when the engine gets overheated, heat tends to transfer to the AC system and blow warm air into your car. To fix this, you need to figure out what’s causing your engine to overheat as soon as possible.

If you have more mechanical know-how, then you can fix it yourself. But if not, then it’s recommended to take your car in to see a professional.

Car temperature gauge overheating

Conclusion

Maintaining a car’s AC system is very important. There are multiple different ways you can keep the AC system functioning yourself, from using a vacuum pump to cleaning your air vents. But if the issue is too big to deal with, then you can also always take your car in to see a professional.

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References:

Off-Roading Pro

Consumer Rating Guide

AUTOMOTIVE AC VACUUM PUMPS CONSUMER RATINGS & REPORTS

Go Mechanic

What Happens When You Don’t Service Your Car AC?

Replicarclub

How to Vacuum Car AC System Without Pump

Hirlinger Chevrolet

HOW OFTEN SHOULD YOU CLEAN YOUR AIR CONDITIONING SYSTEM?

Car Mudi

How Often Should I Clean My Air Conditioning System?

Cars Cost Helper

How Much Does Car Air Conditioning Cost?

Amazon

FJC 6912 Vacuum Pump 5.0 Cfm

HFS R Vacuum Pump Double Stage

Vivohome Dual Stage Rotary Vane HVAC Air Vacuum Pump

Mastercool 90066-B 6 CFM Single Stage Vacuum Pump

JB Industries DV-6E Eliminator 6 CFM Vacuum Pump

Ernest Martynyuk

An automotive enthusiast who's been tinkering with vehicles since I was 15-years old. Repairing automotive electronics has been my main job for over a decade now and have a passion for everything technical regarding cars.

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