How to Service a Car AC (Air Conditioner)

Step-by-Step: How to Service a Car A/C (Air Conditioner)

There is nothing worse than trying to cut on your car A/C on the first warm day of the year only to get lukewarm air blowing or (even worse!) no air at all. The air conditioning system of a car is one of the most complicated systems on the vehicle, and services depend on what part of the A/C system is malfunctioning. 

Servicing a car’s air conditioning system involves diagnosing the part of the A/C system that is not working, determining if the owner can service it, and then repairing the system. Car A/C problems can range from slow freon leaks to seized-up compressors and usually require a mechanic.

A/C repairs usually can’t be performed easily by the car’s driver, but in the case of a slow freon leak, you might be able to keep your car’s A/C functional a little while longer before a professional needs to step in and intervene. Keep reading and learn more about common problems with a car’s A/C system and how you can service them, as well as how to maintain your car’s air conditioning system. 

First Things First – Know Which Car A/C Parts Need Professional Service

Several aspects to a car’s air conditioning system may require maintenance at one point or another during the service life of the car, some more accessible to the driver than others. 

When you look into servicing a car’s air conditioning system, you will typically run into problems in one of the following areas: 

  • A/C compressor: The compressor in a car’s air conditioning unit is responsible for compressing refrigerant freon gas, which quickly heats it. 
AC compressor
  • A/C condenser: Once the compressor has compressed and heated the freon, it is passed to the condenser, where it is formed into a supercool liquid. 
AC Condensor
  • A/C Receiver-drier: The receiver-drier is the part of the car’s A/C system that removes moisture from the air in the A/C system. 


  • A/C evaporator: The evaporator is the part of the car’s air conditioning system that turns the supercooled freon into a refrigerant mist. The air in the car’s air conditioning system is blown over tubes containing a supercool mist to remove heat before blowing it back into the car’s cabin. 


  • A/C hoses: A/C hoses send air and freon throughout the car’s air conditioning system. If these hoses spring a leak, freon can leak out of the car’s A/C system to the point that it no longer blows cold. 
AC Hose
  • A/C blower motor: The blower motor is the part of the car’s air conditioning system that pushes cooled air from the evaporator back into the car’s cabin. 


  • Electrical circuits: If a car suffers from wiring problems, it can sometimes interfere with the car’s ability to trigger the air conditioning system from the cabin instrument panel. This kind of systemic electrical issue is usually caused by faulty wiring harnesses or bad relays. A car wiring diagnostician is typically required to repair this level of A/C malfunction. 


Because these components are often located deep in the guts of a car’s chassis and the engine compartment and sometimes require specialized equipment to repair correctly, these kinds of A/C repairs are usually left to an automotive repair shop rather than attempted at home. 

There are some easy ways to figure out how bad your car’s A/C problems are with a little troubleshooting. Keep reading to determine what part of your car’s air conditioning system is malfunctioning and what you can do to fix it. 

My Car’s Air Conditioning System Is Not Working! A Troubleshooting Guide

So, you go out to your car, turn the key, click on the air conditioning system, and—nothing. Perhaps there is hot air, which can feel even worse on a blazing summer day than no air at all. What do you do at this point? It depends on which symptom your car is presenting with. 

No Air Blowing from the Car’s A/C Unit

AC No Air

If you turn your car’s A/C system on and there is no air at all, this could be a sign of several problems. The worst-case scenario is that the car’s A/C compressor dies. The relatively high cost of the parts involved in replacing this component, plus the intensive labor involved, means that you will likely end up spending between $1,500 and $2,500 at a mechanic’s shop to get your car’s A/C replaced. 

If a car’s A/C compressor has quit, many mechanics will not replace the compressor without using a kit that also replaces other components of the A/C system, such as the condenser and drier-receiver. This is because a new A/C compressor can be damaged by debris from older or damaged parts in the air conditioning system once it is operated. 

If a mechanic agrees to replace the A/C compressor without replacing the associated components of the A/C system, in many cases, they will do so on the condition of the A/C compressor, not receiving a warranty. With a part as expensive as an A/C compressor, it simply is not worth the risk. 

  • NOTE: If you have no air blowing from your car’s A/C fans, it is essential to determine whether or not the car’s radiator fans are running. If the car’s radiator fans are also malfunctioning as the result of an electrical issue, this can lead to the car’s engine overheating (a much more significant repair than the air conditioning system). If there is any doubt as to the function of the radiator or the thermostat, have the vehicle towed to a mechanic.  

Blowing Tepid or Warm Air

AC Warm Air

If your car’s A/C is still blowing but is blowing hot or a little warmer than usual (and is not cooling, no matter the setting), your likely culprit is a leak in the freon system. A slow leak can usually be limped along by recharging the car’s A/C system once a year during the warmer months, but a more significant leak in the A/C system will prevent it from being able to hold freon at all. 

While a car’s air conditioning system is designed to be a closed vacuum system, age can eventually affect the rubber, plastic, and metal components of a car’s air conditioning system until leaks develop as a result of dry rot and other factors. Sometimes a smoke or leak test can be run on the car’s A/C system to see if a specific hose is leaking. If a major leak is found in the system, the hose can then be replaced. 

However, leaks in the A/C system are often slower and occur at disintegrating seals throughout the A/C system. This causes a slow freon leak in which the A/C gets gradually less and less cold until it stops blowing cold air entirely. At this point, the freon in the car’s A/C system must be refilled or recharged. 

Barely Blowing Air

Barely Blowing Air

If air is still blowing through the car’s vents but does not feel as forceful as it should, this can be the result of the air cabin filter becoming clogged. Check the filter in the car’s engine compartment to ensure that it does not require replacement. Once a dirty, clogged cabin air filter is replaced, this can usually restore A/C airflow to the car’s cabin as long as other components are not defective. 

A good time to have your car’s cabin air filter checked is during a routine oil change or a trip check. Mechanics can inspect the air filter and replace the filter as necessary. 

Air Not Blowing Out of All Vents

AC from Only some vents

Another issue that can crop up in the car’s A/C system is when cold air will blow out of one side of the car’s dashboard but not the other side. This is usually the result of an issue with the blend door actuator, a component in the car’s A/C system that mixes hot and cold air to achieve the required temperature of the A/C’s control panel. 

The blend door actuator can be damaged by debris in the A/C system or can become bound because of age or broken linkage. This is one of the few parts of a car’s A/C system that can be repaired individually rather than as a systemic unit. 

Servicing a Freon Leak in a Car’s Air Conditioning System

Servicing a Freon Leak

If your car is starting to blow a little warmer than you’d like, one of the first pieces of advice that you’re likely to encounter is that you need to “top off” your car’s freon. In older cars, this is usually the most cost-effective way to keep a car’s A/C system running for as long as possible without being forced to replace it entirely. 

It is essential to keep in mind that topping off a car’s air conditioning system incorrectly can damage delicate components in the system and inadvertently cause a more expensive repair. Without a pressure gauge and the proper specifications, this is not a procedure that should be undertaken unless you have prior experience in automotive maintenance. 

The safest way to get your car’s A/C recharged is to take it to a mechanic. Here are some typical aspects of a freon recharge service:

  • Typically runs around $200 to $280 depending on the cost of freon and the size of the vehicle.
  • It can usually be performed in a few hours, sometimes while you wait if you secure an appointment at the mechanic’s shop ahead of time. 

If your car has a slow freon leak, a mechanic will usually not just recharge the system with freon; they also add a paginated oil to the system that will show up under a UV light inspection if all of the freon leaks out of the system again. This will hopefully help mechanics discover the direct source of the freon leak and repair it for the next season when the freon leaks out again. 

Tools Used to Diagnose Freon Leaks in a Car Air Conditioning System


Consumer Freon leak detectors are available for those who want to identify if a leak is occurring. 

Mechanics use two major tools other than direct observation to detect and diagnose freon leaks in a car air conditioning system: 

  • Smoke test: A smoke test is performed using a piece of equipment that blows smoke through the car’s A/C system to help mechanics identify any potential leaks in the system where freon might be escaping, such as a faulty A/C hose seal. This is an excellent test to perform for more massive A/C freon leaks. 
  • Paginated oil: For smaller freon leaks, paginated oil is usually included in a freon recharge service along with the freon itself. Not only does this paginated oil help lubricate the A/C system and shows mechanics exactly where potential freon leaks might be hiding by highlighting them under UV detection

In cases where a car’s air conditioning system is running completely hot, mechanics will typically try to discover the source of the freon leak before recharging the system. This is because if there is a significant leak in the A/C system, the freon will be almost immediately lost, and the mechanics will be right back to square one on the vehicle in a day or two. 

Can I Repair My Car’s Air Conditioning System Myself?

Repair AC Yourself

​​​​Freon recharging kits available online and in automotive supply stores will allow you to recharge a car’s freon at home. While this might seem like a convenient alternative to taking your car to the auto mechanic, there are some significant risks involved with working on your car’s A/C system yourself. 

The biggest risk of recharging your car’s A/C system at home is operator error—if you add too much freon or over-pressurize the system, it can permanently damage the A/C compressor. This can turn a thirty-dollar repair into a repair that costs more than the value of the vehicle in some cases. Depending on an individual’s experience in auto repair, this may or may not be a risk worth taking. 

If you do decide to go about refilling your car’s freon on your own, it’s a good idea to read your car’s owner manual carefully and watch several online videos or read several tutorials on how to do it before attempting it on your vehicle. It is also better to attempt a first-time repair on a vehicle with a more experienced mechanic observing and helping out if you can swing it. 

How to Refill a Car’s Air Conditioning System with Freon – DIY Method


Once you decide you have enough automotive repair experience to attempt a do-it-yourself recharging kit, you can pick one up either online or at an automotive supply store. If you buy the parts of the recharging kit individually, you will need to buy two cans of refrigerant (r-134), a refrigerant dispenser, and a pair of goggles for safety since you’re working with compressed freon. 

To recharge the freon in your car’s system, follow these steps: 

  • Verify that your car’s A/C compressor is functioning (if not, there is no point in recharging the system).
  • Find the low-pressure side refrigerant fill port. 
  • Attach the refrigerant dispenser to the fill port. 
  • Recharge the system, monitoring system pressure as you do so.

To recharge a car’s air conditioning system on your own successfully, you must follow the instructions included with your refrigerant dispenser to the letter and make sure that you don’t over-pressurize the A/C system by accident. If you do, you might end up spending significantly more to get cold air for the summer than you anticipated. 

Risks Involved with DIY Freon Refills

common mistakes AC servicing

There are several points in recharging a car’s air conditioning system where you can inadvertently cause damage to the A/C system. Here are some points to keep in mind when you are recharging your car’s freon:

  • If your car has a major A/C leak, recharging the system with freon is a waste of time and money. Within a few days, all the freon will leak out, and the air conditioning will be running hot again. It is usually easier for a mechanic to verify the severity of a car’s freon leak than the car’s owner.
  • The high-pressure side hoses in the A/C system become extremely hot, and inadvertently touching them while recharging the system can lead to a significant burn.
  • Turning the freon can upside-down during a recharge can lead to the transfer of liquid freon rather than gas. While experienced mechanics are capable of doing this gradually with suction lines to prevent damaging the compressor, most DIYers are not. It is not worth the risk to the A/C compressor if you are not 100% sure what you are doing.
  • If you accidentally add too much freon to your car’s A/C system, venting excess freon into the air is illegal per Section 608 of the Clean Air Act. If you believe you have accidentally over-pressurized your system, you will be forced to take it to a mechanic to undo the damage. 

It can be tempting to try to recharge a car’s air conditioning system yourself, especially if you are dealing with an A/C unit in an older vehicle that is not worth much. But unless you are willing to risk losing the air conditioning entirely, it is a good idea to leave A/C refills to the professionals unless you’re confident you know what you’re doing. 

Is It Worth It to Replace the A/C in Your Car?

consider factor when fixing AC

If your car’s air conditioning unit needs expensive service, you might wonder whether replacing the A/C in your car is even worth it. Ultimately, this depends on the age and condition of the vehicle, as well as the climate that it is driven. 

  • Someone who lives in a colder climate might be content to forego air conditioning a majority of the time, but someone who lives in a southern temperature will be much more likely to jump on their A/C repair as soon as it’s necessary. 
  • It also depends on the severity of the repairs needed for the car’s air conditioning. If a car only needs a freon recharge once a year, for two hundred bucks a year, it can be well worth keeping an older car running with a cool air conditioner. 
  • However, if your older car throws an air compressor that will cost more to replace than the value of the car, it is worth taking a second look to see if replacing the compressor is even worth the trouble. 

You could likely find a car of equivalent value with a working air conditioner already for that amount of money. An A/C compressor kit is one of the most expensive repairs on most vehicles, so it is worth considering whether replacing the car entirely wouldn’t be a better option depending on the rest of the car’s condition.

Maintaining a Car’s Air Conditioning System

Maintain AC

When it comes to car A/C repair, the bottom line is that you’re likely going to need to contact an automotive technician to handle any but the most minor of car A/C repairs unless you already have some experience in automotive repair yourself. 

A car’s A/C system can be one of the trickiest systems on the entire car to repair as a layman, and doing it incorrectly can lead to further damage that can potentially turn a job that costs a few hundred dollars in parts into a job that costs a few thousand instead. Most drivers do not have the level of experience to repair a car’s A/C system safely and effectively on their own. 

However, there are many ways that the driver of a car can service their car’s air conditioning system to keep the system in good working order and minimize the need for repairs. 

Here are some of the steps to ensure that a car’s air conditioning system remains working well:

  • Run the air conditioning system at least once a week for at least ten minutes, regardless of the ambient temperature. This will help keep the gas pressure in the A/C system equalized, which in turn goes a long way towards preventing A/C leaks. 
  • Run your car’s defrost mode regularly (at least for ten minutes once a week) to evaporate any excess moisture. This is especially important in humid or damp climates.
  • Replace older A/C hoses or other defective components to prevent freon leaks in the air conditioning system. Usually, multiple air conditioning components are replaced all at once during an air conditioning service to minimize the cost of labor and prevent damage to new parts by older auxiliary components. 
  • Keep items out of the vents. Small children are notorious for pushing pencils and other small knick-knacks into car air conditioning vents, where they can potentially cause damage to the system further down the line. Make sure that your vents remain clear of any debris.
  • Prevent water damage. Water damage in a vehicle from flooding or rain can not only cause mildew in the cabin compartment, but it can also cause mildew in the car’s A/C system. This can lead to damaged components and an unpleasant smell in the vehicle.
  • Change the air cabin filter regularly. Not only does this ensure proper air circulation through your A/C system, but it also increases the air quality in the car’s cabin. Cabin air filters are usually inspected during a car’s routine oil change, but you can request this service if it is not offered.
  • Do not run A/C with car windows down. This forces the car’s air conditioning unit to work much harder than it has to, causing the entire system to age and deteriorate more quickly from the additional workload. 
  • Get your car’s A/C system maintained regularly. Recharging the system every two years once it starts to lose some of its coolness can help you keep your air conditioning blowing ice cold and help mechanics diagnose, identify, and repair more minor problems within the A/C system before they become a considerable expense.

Maintaining a car’s air conditioning system is much easier than trying to replace it, so it’s a good idea to prevent added stress on your car’s A/C if you can make it last longer. 

Once a car’s A/C system is old enough to fail, the car itself is often comparable in value to the A/C repair. This can make repairing the air conditioning on an older vehicle a tough choice, especially when you could buy a used car for roughly the same price or put a down payment on a new one. 

Servicing a Car’s Air Conditioner Can Be Hard for Novices

Because there are so many different components that can break down in a car’s A/C system, and many of them are difficult to access or observe properly without specialized tools and supplies, many services related to a car’s air conditioning system are better left to professionals. It is possible to recharge your freon using a do-it-yourself kit, but those who do this risk damaging their A/C system accidentally. 

Luckily, the low cost of servicing a car’s air conditioning system with a freon recharge every few years is well worth it to keep your ride in cold air.