Car AC Compressor Not Turning On: Causes and Possible Fixes

Your car ac compressor not turning on can be nerve-wracking, especially if you can’t identify the problem. A faulty compressor is most likely caused by an electrical problem. Whatever the problem is, it doesn’t spell total doom as long as it is diagnosed and fixed on time.

Car AC Compressor Not Turning On Causes and Possible Fixes


In this complete guide, our automobile team will discuss several reasons why your compressor isn’t coming on and how you can resolve this problem immediately.

Why Is Your Car AC Compressor Not Turning On?

Your car AC compressor not turning on is caused by a bad compressor system, bad relay, or even a bad fuse. However, these aren’t the only reasons for this issue. It can also be due to low refrigerant charge, an overcharged refrigerant, or inadequate oil lubricant.


An AC cannot work without a compressor. A compressor is a vital component of your car’s cooling system; without it, your AC won’t start. It is just as important as the car’s engine for your performance. Here are other possible causes of a compressor refusing to come on.


– Low Refrigerant Charge

Believe it or not, refrigerants affect the performance of your car AC, and a low charge shouldn’t be ignored. These charges determine the refrigerant levels of your car AC, and every AC unit has a range it shouldn’t exceed or get lower than.

A leak is a common cause of undercharged refrigerants. A leak causes your compressor to lose cooling power and generally perform below normal. For example, when you have an undercharged ac refrigerant, you’ll notice that your car AC will start to blow hot air. You may also notice a weird humming or hissing sound from the air conditioner’s compressor.

– Overcharged Refrigerant

To avoid having a low charge, you may think overcharging makes it better, but that’s not true. For many, overcharging the refrigerant means having more cool air. But, on the contrary, an abnormally high charge will cause your air conditioning system to produce hot air even when it should cool the air.

Some symptoms of an overcharged refrigerant include liquid leaking into the compressor, overheating, and unpleasant noise. If this goes unchecked for a long time, your compressor might eventually shut down completely.

– Faulty Car AC Pressure Switch Sensor

If your notice your car’s AC is refusing to come on, this could be caused by a bad pressure switch sensor. A pressure switch sensor controls the car AC pressure levels, controlling when to enable or disable the compressor when you select the “Heat” or “Cold” setting. In other words, a switch sensor is similar to climate control as it allows you to set the temperature of your car automatically.

When you have a faulty switch sensor, you’ll notice that your car’s AC becomes irregular, starting and stopping on its own periodically. You may also find that the air conditioning system is blowing hot air or hear a humming sound from the vent. If this continues for a long time, your compressor will eventually refuse to turn on.

– Dead Compressor

If your car’s air conditioning compressor is not turning on, another common culprit is a dead compressor system. When your compressor is quiet, there’s no way your car cooling system will work unless it is replaced. Most times, your car displays symptoms of a failing compressor which is often ignored due to ignorance.

If you notice your car blowing hot air or making unusual sounds when the AC is turned on, it is a sign that your compressor is failing. If you have issues with your compressor clutch getting stuck intermittently, it is another indicator of a bad compressor. When these signs are left unchecked, having a dead compressor is inevitable.


– Wiring Issues

Yet another reason why your compressor isn’t turning on is that it has wiring issues. Several factors can cause wiring issues, and one of the most common is an error during repairs. If you’ve had to carry out repairs on your car, the mechanic could have crossed some wires, affecting your AC’s performance. On the other hand, if your vehicle is relatively new and the compressor isn’t turning on, it could indicate a mistake during internal installation.

Another cause of a wiring issue could be rodent damage. Mice can cut through your wires with their teeth and disconnect important wires. When this happens, you will notice that your compressor will start to malfunction.

– Compressor Clutch Isn’t Engaging

Your AC compressor comes with two important components: the AC clutch and shaft. When the AC compressor is turned on, the shaft starts to rotate, and the clutch is immediately engaged to the shaft. When your AC clutch engages the compressor shaft, the temperature in your car will significantly start to cool. If your compressor clutch isn’t engaging, then the compressor will likely not turn on.

Even when it turns on, there’ll be no reaction as the clutch hasn’t been engaged. There are several reasons why your AC clutch won’t engage, and one of them is a bad or rusted clutch plate. Other causes include a worn or damaged serpentine belt, a faulty AC switch, or inadequate refrigerant levels.

Blown Fuse

Having bad fuses is a common electrical issue and another reason why your air conditioner compressor is refusing to turn on. A damaged fuse harms your air conditioning system as it will become unresponsive. In addition, high currents, inadequate refrigerant levels, and wiring issues can cause a damaged fuse.

Aside from your compressor not turning on, there are other telltale signs of a bad fuse, including difficulty in starting your car engine. In addition, your check engine light might come on, and over time, your car may refuse to move when on transmission.

– Bad Relay

Your AC system is powered by a compressor relay which powers the compressor and its clutch. In turn, the AC system is activated into blowing cold air. When the clutch relay becomes bad, the first sign of this is your compressor will refuse to turn on. You may also notice that your AC produces inconsistent cooling air and may even go off completely at some point.

– Contaminants in the System

Like every other part of a car, contaminants will always make their way in, and when these find a home in your system, they disrupt the optimal performance. These contaminants can be corrosion, residual matter, grease, debris, or worn oil. Another common source of contaminants getting into the system is a clogged or worn out filter-drier.

A filter-drier functions by trapping contaminants and moisture present in the AC system. When this doesn’t work as it should, contaminants will thrive in your system, resulting in an unresponsive compressor.

– Inadequate Oil Lubricant

Every machinery needs lubrication to function well, and the car air conditioning system is no different. The right amount of oil in the compressor not only aids its smooth operation but prevents the compressor from overheating. It also keeps other system components well-oiled to prevent corrosion and rust. When this fluid becomes inadequate, it is inevitable to have issues with your compressor, one of which is unresponsiveness.

Another sign that your compressor lacks enough oil is when you notice a burning smell and noise coming from your compressor. Sometimes, you may notice your car emitting too much smoke when your AC is turned on. All of these indicate inadequate oil lubrication, which needs to be fixed immediately.

– A Bad Battery

A bad car battery can cause your vehicle’s compressor not to turn on as it doesn’t have the right amount of charge needed to power the compressor. A faulty battery could be a result of the battery being old or not properly charged. When this is the case, the battery might be able to power your engine but won’t have enough voltage needed to run your AC unit.

How Do You Fix AC Compressor Not Turning On?

To fix AC compressor not turning on, you can start by making sure it has the correct refrigerant levels, lubrication, and working wires. You can aso try replacing the dead compressor, fixing or replacing the compressor clutch, or cleaning the filter-drier.

Fixing AC Compressor Not Turning On


Regardless of how often it is used, an automobile AC Unit compressor can last up to 10 years. Although the longevity of your compressor is largely determined by how much it is used, compressors are known to last for a long time. If you maintain your compressor and carry out routine checks as often as possible, it could last longer than ten years. It isn’t surprising to find a compressor lasting more than ten years.

Aside from these, there are other ways you can fix this problem, and they include the following:

– Ensure Adequate Refrigerant Levels

Having an undercharged or overcharged refrigerant can affect the smooth performance of your compressor unit. Hence, you have to ensure your fridge has the required level of refrigerant needed to function properly. You can refer to the manual or guide that came with your car to check the acceptable range of refrigerant for your car model.

If the manual lacks this information, you can reach out to a professional mechanic who will be able to gauge a suitable refrigerant level for you. Once the compressor has the right amount of refrigerant, there’s a high chance the compressor will turn on and start working perfectly.

– Repair Pressure Switch Sensor

If the switch sensor is the cause of your compressor refusing to work, you’ll need to get it fixed. Although most switch sensors can be repaired, we recommend replacing them with a new one to avoid dealing with future cases of failure. Changing a switch sensor is not so complicated if you have technical knowledge. All you have to do is to locate the sensor and disconnect the negative battery cable.

Once this is done, loosen the electric connector surrounding the sensor and gently remove the sensor with a wrench. Next, install the new switch and make sure it is tightly screwed. Once that is done, screw the electrical connector back on and reconnect your negative battery cable. After this is done, switch on your AC system to be sure your compressor can turn on.

– Replace Dead Compressor

Most times, a dead compressor is better off being replaced than being repaired, as repairs would cost more money than a replacement. Although replacing a compressor isn’t so hard, it can be a long process and many factors can go wrong if you are not very careful.

Once you’re sure that a dead compressor in your AC system is unresponsive, immediately contact an authorized automobile repair service to come and fix the problem. If you think you can fix it yourself, follow specific instructions for replacing the compressor to avoid causing damage to other important components of your vehicle.

Your AC probably isn’t cooling due to compressor issues or inconsistent refrigerant levels. You can fix this by fixing or replacing the compressor or parts that need urgent repairs. You should also make sure the compressor isn’t filled with contaminants, or that it has the right amount of oil needed to function properly. Also, ensure that the relay and electrical connections are all working optimally.

– Check the Wiring

Since damaged wires are another reason why your compressor could not be coming on, you’ll have to carry out checks on your wires. Inspect each one to ensure they have not suffered rodent damage or been disconnected from where they should be.

Also, ensure that all wires are correctly connected, tightened, or installed properly. If you notice any irregularities or issues with the wires, contact your mechanic to help fix this problem to prevent it from affecting other parts of your car.

– Fix or Replace Compressor Clutch

If your compressor clutch doesn’t engage or is damaged, you must fix or repair it accordingly. The first way to fix a bad ac compressor clutch is to check the refrigerant level to ensure it is right. Also, check that the lubrication is sufficient. If, after doing this, the compressor clutch still doesn’t engage, you may need to jumpstart the clutch.

Jumpstarting a clutch allows it to engage the shaft manually, but this could be potentially dangerous if you don’t know how it works. If it doesn’t work, you must check for any electrical issues affecting your AC system. You may have to replace the clutch entirely if none of these work.

– Check AC Electrical Circuit

Damaged fuses can affect your compressor’s performance and make it unresponsive. If you’ve checked and everything seems perfectly fine, check the electrical circuit and capacitor to be sure there is no damaged fuse.

If you discover a damaged or even a worn out fuse, you must replace it with a new one. Doing this will likely resolve the issue of your compressor not turning on, and if it doesn’t, contact a mechanic for a proper diagnosis.

– Fix Compressor Relay

Once you’re certain that the compressor relay is why your compressor isn’t turning on, it’s best you get it fixed immediately. One way to do this is to clean the relay contacts, which can be clogged with residual matter and dirt, causing them to fail. Another way to fix a bad relay is to replace it completely if it doesn’t work after cleaning and repair. A new relay should get your compressor up and running in no time.

Nonetheless, we also advise car users to use their AC units less frequently, as this will ensure the longevity of the compressor relay. Carrying out routine maintenance will also prevent your relay from getting stuck or failing.

– Clean Your Filter-Drier

Filter-driers help filter refrigerants and trap moisture or contaminants from finding their way into the AC unit. Always make sure these are kept clean as often as possible. We advise routine checks and maintenance on your filter-driers every six months for optimal safety. In the same vein, keep your air filters clean and ensure they are not clogged, as these can also affect your compressor.

Cleaning Car Filter Drier

Take note that it isn’t safe to spray wd40 directly on your compressor. Spraying wd40 or any cleaner on your compressor will likely cause it to malfunction. Compressors do not directly need any form of cleaning maintenance; carrying out routine checks is enough.

– Ensure Adequate Oil Lubrication

Oil lubrication is very vital for the smooth operation of your compressor. As stated earlier, it keeps the compressor running perfectly and is a cooling agent that prevents it from overheating. Make sure your compressor has the right amount of oil needed to function. Replace or top it off if the oil is worn or insufficient.

In the same vein, avoid excessive oil lubrication because this can cause too much friction, leading to compressor seizure. Too much oil can drown the evaporator coil and diminish its ability to absorb heat from the compressor. You also must ensure you only use high-quality automobile oil for your compressor to avoid future problems.

– Manually Engage the AC Compressor

You can manually engage the clutch on your compressor manually by jumpstarting the compressor. You can also use your clutch to engage the shaft manually by jumpstarting the condenser or AC.

However, this isn’t a safe option unless done by a professional. It’s recommended that you replace your failing clutch than jumpstart to avoid causing unknown damage to other parts of your car.

Conclusion of Car AC Compressor Not Turning On


Now that you know what might be causing your vehicle’s compressor not to turn on, you don’t have to worry and can get started on troubleshooting this. Here’s a recap of the key points discussed in this article.

  • Your car AC compressor not turning on is likely caused by issues concerning the compressor and its clutch.
  • Other possible reasons include bad wiring, damaged fuses, a clogged or worn filter drier, as well as an inconsistent level of oil lubrication.
  • You can solve this problem by fixing all issues concerning your compressor and clutch, especially its switch sensor and relay.
  • You should also check your wiring and electrical circuit to be sure it’s working properly. Also, clean your sensor and replace/top off oil when necessary.
  • To make sure your compressor lasts longer, use your AC less frequently and always carry out regular maintenance.

We hope that we’ve been able to help you pinpoint the exact cause of your compressor’s unresponsiveness. Then, with our corresponding list of solutions, you should be able to resolve this problem in little or no time!

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