Car Air Conditioner Repair

Car Air Conditioner Repair

How a Car Air Conditioning System Works

How AC Car Works

The AC in a car works in a similar way to the air conditioning unit in your home. It cycles refrigerant through the coils in the vehicle.

The refrigerant is a cold substance that air is blown over before being blown into the main cabin. The liquid is in a pressurized state once it goes through the compressor which propels it through the cyclical system.

As the refrigerant warms up, however, it is no longer useful in cooling the air. It is cycled through the coils until it reaches the condenser. The condenser cools the refrigerant, absorbing the heat from it, so that it can be cycled back through to cool the air being blown in the cabin.

Before it can cool the air that is being blown into the main cabin, however, it must first go through the compressor, which re-pressurizes the refrigerant and sends it back into the system. This turns the refrigerant back into a liquid so that it can effectively cool the air that is going into the main cabin.

This liquid is turned into a mist so that it can cool the tubes or coils in the AC, which in turn cools the air as it blows past this area, aptly known as the evaporator, and into the cabin.

Moisture from the refrigerant and air blowing through the system is collected in a drip-pan known as the accumulator, allowing the air inside the cabin to be dry, not humid. Cold, humid air produces an unpleasant, clammy feeling.

What Causes AC to go Out in a Car?

Because there are a lot of moving parts in a vehicle’s air conditioning system, there can be several different ways that it can go out.

Learning how to diagnose the issue can be tricky, because not only are AC systems different depending on the year of the vehicle, but different models also tend to have different parts.

Furthermore, the problem may be mechanical, or it could be electrical. Older vehicles tend to have AC systems that are purely mechanical, while more modern vehicles could need repair in mechanical or electrical areas.

Failed switches, a leak, or issues with the compressor are the most common causes of an air conditioning system going out in a vehicle, no matter the make and model.

How Do I Fix the AC In My Car?

Scheduling routine maintenance at a mechanic is the best way to get ahead of potential issues with your vehicle. (1) During these routine visits, a mechanic will check over different areas of the vehicle and look for signs of damage or potential for damage.

If they find anything wrong with the AC system, they’ll either replace or repair the part, or notify you of a potential upcoming problem with the system.

[…] regularly scheduled preventative maintenance is the key to avoiding the unexpected breakdown of an HVAC system at a later date.


Fixing the air conditioning unit in your car can be difficult on your own, even with mechanical experience. Depending on the make and model of the vehicle, the system may be easily accessible from underneath the hood of the vehicle, or it could be accessible only through the bottom, which will require the vehicle to be suspended in the air for work to be done.

Main Causes of Weak AC Air Flow

Weak AC Air Flow

If you are experiencing weak air flow from your car’s AC unit, it means that something is blocking the flow of air from the outside into the main cabin.

There are many possibilities for this type of issue, and the cause should be identified before pursuing repairs.

A blocked or dirty air filter is one of the most common causes, as many people neglect to change their air filter regularly.

A faulty fan is the second most common cause, as the unit would then be reliant on just the air coming in from outside as the vehicle is moving, rather than the internal fan forcing air over the cooling coils.

Mold or mildew growth is one of the more concerning causes that could be hindering the flow of air, as spores or particulates can be spread inside the main cabin if there is too much moisture buildup. In addition to a weak air flow, the air may feel clammy or damp; this means that the moisture from the air outside is not being dried well enough, and the accumulator provides an excellent environment for mold and mildew growth.

Causes of Lack of Cold Air

Now that you know how an air conditioning system works in a vehicle, it might seem obvious that a lack of cold air is most often caused by a lack of refrigerant in the system. This typically occurs only if there is a leak in the coils where refrigerant passes through.

It can, however, be caused by other issues as well. A broken or clogged condenser may be the culprit, as the refrigerant can’t re-cycle through the system. This often results in a quick blast of cold air that warms quickly.

Warm air may also blow from the AC if the compressor does not engage, allowing the refrigerant to cool and pressurize enough to turn into a mist that cools the coils.

This lack of compression can be a symptom of an electrical problem as well, especially in newer models of vehicles that are increasingly reliant on electrical systems. Fortunately, a quick run through a diagnostic tool is typically enough to discern this without taking the unit apart.

Causes of Stale Odors

While this is not as common as the other issues, it’s still a difficult problem to grapple with, as no one wants to smell foul odors throughout their daily commute.

The most common cause of stale or musty odors in the AC system is mold or mildew present somewhere in the system. This may be in the accumulator, or it may be a problem with the desiccant failing to dry the air enough as it enters the system from the outside.

This is an especially common problem during and after fall, as vehicles with leaves under the hood may be clogging the system. These leaves can easily hold moisture and begin rotting in the system, causing the stale or unpleasant smells that travel into the main cabin.

If this smell is present even without the AC system running, however, it may be the presence of mold or mildew in the interior carpeting of the vehicle, or a leaky trunk seal that is allowing moisture or debris to enter the trunk area.

How Often Should a Car’s AC Be Checked?

While it’s best for your vehicle’s AC system to receive a check-up with the rest of the vehicle on a seasonal basis, it should be done at least once every year. Harsh weather can be a detrimental factor in the health of an AC system, putting a lot of strain on the heating and cooling system overall. (2)

If possible, a vehicle’s AC should be checked seasonally, or with your routine oil changes to keep the filter and temperature control system in check every 3,000 miles or every 3 months.

Be sure to change your cabin air filters every 12,000 to 15,000 miles to ensure a clean ride.


While this might seem like an excessive amount of upkeep for an air filtration and cooling system, it helps to prevent any mishaps or breakdowns when you need cooling the most. Driving during a hot summer when your vehicle won’t blow cold air – or worse, constantly blows hot air – is never a fun experience.

Signs Your AC Is Going Out

If you start noticing anything unusual with your AC system, it might be a sign that you should seek car air conditioner repair services. Staying vigilant about how your vehicle is running and getting familiar with all the sounds and feelings that it brings with it during typical operation is an important step in keeping your vehicle healthy and extending its overall lifespan.

A lack of air flow – or a weakening air flow – is one of the most common signs that your AC unit is starting to go out. This may be accompanied by strange sounds, which may just be a leaf stuck in the vent, but it could also be the unit failing. This is a sure sign that it’s ready for a check-up, at the very least.

Foul odors and damp air coming through the system into the main cabin is another sign that your AC system needs replacement rather soon, as these indicate that part of the unit is already non-functional.

Finally, a lack of cool air entering the cabin means that something has malfunctioned or broken inside the system and it’s not only past time for a check-up, but it may be time to replace parts of the unit.

Common Car Air Conditioning Problems

It’s important to always stay on top of your vehicle maintenance, even if you don’t drive it often. It is an essential part of car ownership and will help extend the lifespan of the vehicle and save money on car repairs over time.

The most common car air conditioning problems that wind up needing repair are listed below, which can be the cause of some of the symptoms and problems discussed in this article.

A faulty cooling fan is a relatively inexpensive fix for most vehicles, and it can cause a weakened and warmer air flow into the cabin. This prevents the air from outside from properly blowing across the cooling coils and into the cabin. Left unresolved, it can also cause the refrigerant to get too cold, causing further damage to the system.

A problem with the unit’s condenser is another common problem, most often caused by neglecting routine maintenance. Unfortunately, the condenser is an expensive fix, but many come with manufacturer warranties that can help replace the unit if it has been properly maintained.

Electrical issues are another common problem that cause a lack of cooling, resulting in acid build-up that corrodes the system if left unchecked.

Will it Hurt to Keep Running an AC That Blows Hot Air?

It is never a good idea to keep an AC running if it is not functioning properly, and this includes blowing hot air instead of cold air.

If the unit has not been well-maintained, there is a possibility of it becoming a fire hazard, especially in hot weather where the unit is already strained to operate at its baseline.

Depending on the problem causing the AC to blow only hot air, it can either damage the unit further as the refrigerant lines are clogged and eventually create a leak or damage the compressor or burst the lines in the unit.

Furthermore, if your vehicle is lacking refrigerant and the AC continues to run, it can cause various parts in the system to burn out, as it runs dry.

If any of these symptoms appear, it’s important to bring the vehicle to a mechanic so the problem can be fixed as soon as possible to prevent further damage to the system. This is especially important if the vents into the main cabin are not operating correctly, causing the AC to continue blowing hot air into the cabin despite it being “closed” from the cabin’s side.

Is it Worth it to Replace AC Compressor?

Yes, it’s always worth it to replace an AC compressor as the unit is an integral part of the air conditioning system. Without the compressor, the vehicle will not be able to supply cold air into the main cabin.

Unfortunately, the compressor is an expensive item to replace, which means it may be worth looking into the manufacturer’s warranty if it is still valid. These warranties are often valid for a few years from the installation of the unit, and valid so long as it has been properly maintained at a mechanic’s shop.

In other words, if the unit has failed because of a lack of maintenance, then that’s considered negligence on the vehicle owner’s behalf, not the manufacturers. The manufacturer, however, will take responsibility for the unit if it is in good condition but still failed because of a mechanical problem within the unit itself.

How Can I Tell if My AC Compressor is Bad?

There are a few ways you can tell if the AC compressor is bad, and a visit to the mechanic’s shop will help you confirm the diagnosis.

A weakened air flow, or a failure to blow cold air into the main cabin are two of the most noticeable effects that a failing compressor can have. It can also manifest as a difficulty getting the unit to start, or the AC system is making unusual noises.

Unusual noises count as everything from a rattling to a screeching, growling, or clunking noises during operation. If these noises only occur when the unit is running, it’s time for a check-up to diagnose the issue, as it could be a bad compressor, or a blockage that is about to cause damage to the system.

Troubleshooting Car AC Issues

Trying to diagnose air conditioning problems in your vehicle by yourself is often difficult, so it’s best to seek the professional opinion of your local mechanic. No matter how mechanically skilled you are, or how much of a DIY-mindset you might have with home projects, your vehicle is a complex system that has many parts working together. A DIY fix on one problem may lead to another, larger problem down the line.

The mechanic’s shop has the tools and equipment on hand to diagnose the issue quickly and efficiently, ensuring that you fix the root cause of the problem rather than just the symptoms – or worse, the wrong thing entirely.

Don’t Guess… Get Professional Car Air Conditioner Repair

We all know how frustrating it can be to have a clogged or broken air conditioning unit in your vehicle. From annoying whirring, to blowing out hot air when you most need a blast of cold during summer, the range of problems can go on.

While preventative maintenance is the best way to prevent unnecessary repairs, both require a specialist to help you fix the problem.

If you are looking for an air conditioner repair service near you, look no further than Same Day Pros. We help you find experts ready to fix your air conditioners today.

Simply select your state and desired service, and we’ll connect you with an HVAC professional.


  1. Forbes, Property Owners: HVAC Preventative Maintenance is More Important Than Ever,
  2. HuffPost, How to Keep Your AC From Affecting Your Health,

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