AC Compressor Not Turning On (All Causes & Solutions)

Your AC compressor is a critical component in your air conditioner responsible for cooling the air, so if it’s not turning on, then you’re going to get no relief from the hot weather. This is really frustrating in the summer months when you are desperate for fresh cold air.

Well, every problem has a solution, and in this guide, we’ll explain why your aircon compressor isn’t running and how to get it functioning again.

Why Is The Compressor Of My Central AC Not Turning On? (Causes & Solutions)

Here’s a quick breakdown of the most common reasons your compressor won’t turn on. Keep in mind that any steps involving refrigerants will require a licensed professional to help.

Low Refrigerant Levels

Refrigerant is used in your AC to cool the air, and Freon is the most common refrigerant used in modern air conditioners. However, if the level of Freon gets too low, then it will be detected by the AC, and the compressor won’t kick in.

To solve this, you’ll need to refill the compressor with refrigerant and see if this solves the issue. If you notice the refrigerant levels are dropping too quickly, there may be a leak somewhere in the internal mechanism. Colored gas can be used to find the leak, but you are usually better off consulting a professional that uses HVAC refrigerant leak detectors because a leak can be difficult to find and fix by yourself.

Faulty Sensor Switch

Many home ventilation systems provide hot and cold air, and you’ll need to alternate between them. There’s usually a sensor within the AC which detects if you need hot or cold air, or a manual switch to change the settings. Unfortunately, this can become faulty, which means that even if your compressor is working, it won’t be getting the signal to switch on.

If you have examined the compressor and think everything is working, then you need to check the switch. If it looks damaged or isn’t functioning correctly, then you’ll have to replace it.

Dirty Condenser Coils

A lot of air passes through your AC, and that brings a lot of dirt and debris along with it. Over time, this dirt can build up in the machine and cause internal damage and blockages. If this dirt blocks the vents or covers the condenser coils, it can cause the compressor to overheat, which will trigger the automatic safety shut-off to stop your AC from becoming damaged.

If you leave this issue for too long, your whole compressor may give out on you. You’ll need to open up the AC, replace the air filters, clear any blockages, and wash and clean the condenser coils regularly to avoid this issue.

Blocked Valves

Compressor valves help control the flow of refrigerant within the compressor as it transforms from liquid to gas. Valves within your compressor can become blocked by debris or frozen liquid, which can accumulate in the machine. It can also be caused by an issue with the refrigerant where it’s staying in a liquid state instead of a gas in the compressor.

To resolve this, you’ll need to check each of the valves for any blockages and remove them. In some cases, you’ll need to replace the whole valve, and you should make sure the refrigerant is at the right level.

Incorrect Suction Line Size

If your suction line isn’t installed at the right size, it means your AC has to work harder to achieve the same results. This generally means you’ll end up with too much or too little pressure. This, in turn, will indicate your compressor is working inefficiently and can put a strain on the AC.

The only way to resolve this is to install the correct sized line. If the AC was installed before you arrived or is difficult to access, you might need professional help to get it right.

Too Much Refrigerant

Having too much refrigerant can be as much of a problem as having too little. This causes the liquid refrigerant to flood the compressor in a process known as slugging. This can cause many problems and will eventually cause the motor to burn out because it has to work much harder.

You’ll need to drain some of the refrigerant out of the AC to get it working again. By law, this will need to be done by a professional.

Refrigerant Charging for AC

Electrical Problems

Your AC needs electricity to run, and the compressor won’t work if a wiring issue impacts the power supply. You can normally tell if there’s an electrical fault because the entire AC won’t turn on. If this is the case, you should check the fuses and see if any need to be replaced. You should also ensure that the voltage is correct, so the AC is getting enough power from the outlet.

If the AC is turning on but the compressor isn’t, then you’ll need to open it up and look for any loose wiring. Inspect the capacitor and replace anything that looks worn. If the problem persists and you think it’s electrical, then you should consult a professional.

Contaminants In The System

Dust, oil, mold, water, and rust can all contaminate your AC and cause issues with the compressor. They can block up the device and cause your compressor to overheat, which will eventually stop it from turning on at all.

It’s difficult to remove these contaminants once they get into the machine, but you can clean the AC using compressed air to blow the contaminants out. Make sure that you have good filters installed and that you replace them regularly to keep contaminants from clogging up the conditioner.

Insufficient Oil Lubricant

Compressors require constant lubricant, or friction will cause damage to the whole AC. If there isn’t enough oil lubricant, the compressor will overheat until eventually it’s unable to start.

Checking and replacing the oil in your compressor every 6-12 months will help keep your compressor working as it should. There’s usually an accessible container for the oil located near the back of the AC, but you can consult the user manual if you’re not sure.

What Happens When Air Conditioner Compressors Stop Working?

If your air conditioner compressor isn’t working, it won’t always stop your whole AC from running, but it will prevent it from fulfilling its function. The air being drawn into your AC won’t be cooled at all, so it will blow straight back out into the room. This means your air conditioner will be blowing hot air around your room and can actually make the room hotter, the exact opposite of what you want.

Your air conditioner can also become noisy and make loud rattling sounds if the compressor is broken. If left untreated, the issue can compound upon itself until your AC stops working entirely.

A broken compressor is relatively serious. If it can’t be fixed, you will probably have to replace the whole air conditioner because compressors are one of the most expensive components. This means you’ll have to shell out hundreds of dollars and go without cool AC until you can get another device installed.

How To Prevent Central AC Compressor Problems?

Taking steps to manage and maintain your AC compressor is a great way to save yourself a lot of money and the inconvenience of replacing it. Here are a few things you can do to keep it working as it should:

Run The AC

You should aim to run the AC for 10-15 minutes every few weeks regardless of the temperature. This will help prevent any freezing or blockages in the compressor and keep it working properly.

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Clean The AC Monthly

Your air conditioner needs to be cleaned regularly so that dirt and debris can’t build up. Use compressed air to blow away any dust or potential blockages and remove the compressor to wash it down. Check the filters and replace them every 12 months (or more regularly if needed). This will help to stop any contaminants damaging the compressor and prevent the AC from overheating and shutting down.

Get An Annual Check Up

Your air conditioner is an important appliance in your home, so you want to make sure it continues to work properly. How often do you service your HVAC or AC unit? Booking an annual check up with an HVAC professional will help identify any problems early, and they can recommend any action needed to protect your compressor. They will also check your refrigerant levels and adjust them if needed.

People Also Ask (FAQ)

How long does a central AC compressor last?

A properly maintained central AC compressor will last 12-15 years, depending on how often it’s used.

Can only the central AC compressor be replaced?

If you have an issue with the compressor, replacing the whole AC can often be of better value. If the compressor costs more than 50% of a new AC, then you should just invest in a new machine. Make sure you check the warranty because your compressor may be covered, and you can replace it for free within a specific timeframe.

How much does it cost to fix a bad AC compressor?

It costs anywhere from $1,300-$2,700 to fix or replace a bad AC compressor depending on the exact issue and the area you live in.

How do you reset an AC compressor?

Most air conditioners have a reset button which you’ll need to use to reset the compressor. It’s usually red and located near the bottom of the AC. Turn the AC off, leave it for 30 minutes, press the reset button for 3-5 seconds, and then turn it back on. This should hopefully have reset the machine.

Can you run the AC if the compressor won’t turn on?

Yes, the AC will still run, but it won’t be cooling the air, so warm air will blow around your home.


Your compressor is one of the most important parts of your air conditioner, and if it stops working, your AC becomes pretty useless. There is normally an easy way to resolve the issue, but getting into a routine of regular maintenance with your AC can keep your compressor running much longer and protect your cold air supply.

Hopefully, this article has helped explain why your compressor can have issues, and you now have a better idea of how to keep it running properly.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.