Air Conditioner Compressor [Problems & Solutions]

One of the most critical parts of an air conditioner is the compressor, and it ensures the unit keeps producing cold air. This article discusses possible problems with an air conditioner compressor and standard solutions.

Table of Contents

Air Conditioner Compressor Making a Buzzing Noise – Quick Fix

First, ensure the buzzing noise is not coming from the fan motor. If it does, check the blades and test the motor. If the fan checks out, the compressor may be the source of the noise.

The noise may indicate that the compressor is failing. Correctly diagnosing a compressor can be tricky, so it is best to hire a professional HVAC technician to check and repair the compressor if necessary.

Air Conditioner Compressor Not Turning On – Solved

A few factors can cause the compressor of an air conditioner not to turn on:

1. Power Issues

Inspect the wiring between the indoor and outdoor units. There may be a loose connection, or the breaker may have blown a fuse. The circuit breaker may also be tripped, causing the compressor not to work. It is possible for the fan to run while the compressor remains off due to an issue with the power connection.

You may need the services of an HVAC technician to check the wiring and power connection. That way, you can correctly determine if the issue is from the connection or internal components.

2. Dirty Air Filter

Check the air filter to determine whether or not it is significantly dirty. If it is, remove and wash the filter, leave it out to dry, and put it back into the air handler. And if the filter is old, it cannot function at filtering the air and may allow debris to clog the evaporator coil, leading to other problems in the unit. Replace the old filter.

When the filter is filthy, it will restrict airflow into and out of the air conditioner. The reduction in airflow will trigger the compressor to run constantly, which only causes it to overheat and stop working overtime. The compressor may stop turning on to protect itself or due to internal damages.

3. Condenser Coil

Open the outside unit and inspect the condenser coil if you have the required training. A significant amount of dirt on the coil points to why the compressor is not turning on, so it is crucial to clean it.

Carefully remove the dirt and leaves that may be clogging the fins and wash the condenser with a garden hose. Do not use the highest force because it may destroy the fragile fins. Allow the condenser to dry completely before replacing the cover and turning on the unit. Alternatively, employ a professional to clean the condenser.

A dusty condenser coil becomes insulated and traps heat in the outside unit with the filter. The compressor will overheat and shut down to prevent damage. If the trend continues, the compressor may wear out before it should and stop working entirely.

4. Defective Capacitor and Relay

If the relay or capacitor is faulty, the compressor will not have the necessary power to turn on and run. The capacitor and start relay supply the compressor with the power it needs to start and run. So, the repair for a compressor that is not turning on may be as simple as replacing a faulty relay, capacitor, or both.

Remove the start relay and run a continuity test using a multimeter. If you find no continuity, replace the relay. Do the same for the capacitor and replace it if there is no continuity. Sometimes, you may notice that the capacitor is bulging, which is a sign that it is damaged. The same applies if it is leaking fluids.

Note: Many air conditioners function with different capacitors. The fan usually has a separate capacitor from the compressor, so you may find the fan running when the compressor is not.

5. Damaged Compressor

Wear and tear can cause the compressor to stop working, especially if the air conditioner is old. Also, overheating or poor maintenance affects the compressor and other parts. 

However, you cannot be sure of this unless you run a test on the compressor. Therefore, hire a certified service technician to check the compressor and recommend a permanent solution.

Note: If the indoor and outdoor units are not correctly matched, you may find that the compressor has difficulty turning on most of the time.

How Does an Air Conditioner Compressor Work?

The compressor in an air conditioning unit is responsible for compressing the refrigerant, which cools the air in a room. Typically, an air conditioner draws air through the vents and passes it over the evaporator coil. The coil can cool the air because of the refrigerant, which absorbs the heat in the air and leaves it cool.

The refrigerant, which is hot at this point, flows out of the evaporator coil to the condenser coil outside. And from there, the condenser dissipates the heat into the atmosphere with the help of the condenser fan.

However, the refrigerant that leaves the evaporator is in the form of gas at low pressure. The refrigerant cannot release the heat it has absorbed from the room air in that state. In other words, it needs to become a high-pressure gas. For this to happen, the refrigerant flows to the compressor, where the compressor tightly compacts the molecules in the gas and increases its pressure and temperature.

Usually, heat moves from hot or warm areas to cooler ones. So, since the refrigerant is now hot, it will flow out of the compressor to the outdoor condenser because it is a cooler area. Then, the condenser coil releases the heat from the unit.

Testing an Air Conditioner Compressor

The following are steps to test the compressor of an air conditioner:

Press the Power button on the air conditioner and disconnect it from electric power. Remove the cover from the condensing unit and disconnect the relay from the side of the compressor. Next, get a multimeter and set it to Ohms. Then, check the resistance on the windings.

If the motor is good, the reading from pin 1 to pin two should be three Ohms, pin 2 to pin three should be six Ohms, and pin 1 to pin three should be nine Ohms. The lowest resistance reading must be lower than ten Ohms; this is usually the run winding. 

The next highest reading must be two to four times the lowest resistance reading; this is the start winding. Finally, the highest resistance reading must be the sum of the resistance of the run and start windings.

If you find an infinite resistance reading on your multimeter, it indicates the compressor has an open circuit. The same applies if the resistance reading on the multimeter is higher than the stated values. But if the Ohms resistance reading is zero, there is a short in one of the windings.

An open circuit or winding may be due to overheating and not an internal fault. Feel the compressor and if it is scalding, hose it down to reduce the heat. Do it carefully, bearing in mind that it can get damaged by water. Then, recheck the resistance measurements; you may find that they are correct this time.

However, if you find that all the resistance readings are correct, do the following:

Take your multimeter and set it to the highest Ohms range. Next, place one of the multimeter’s test leads on the condenser’s metal case. Ensure you make good contact with the case; scrape dirt or rust off the condenser case to make it easy. Then, measure the pins to the ground. 

If the multimeter does not show an infinite reading, there is a grounded winding, which means the compressor is faulty and may need a replacement. Sometimes, it may mean replacing the entire condensing unit because it is more cost-effective.

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How to Replace an Air Conditioner Compressor

It is ideal to hire a professional and certified HVAC technician to test your air conditioner compressor and determine whether or not it needs a replacement. If it does, the technician is in the best position to replace it.

However, if you have the training to do the job yourself, you will need a new compressor that matches your air conditioning system. You will also need refrigerant, blower torch, hand tools such as screwdrivers and wrenches, a recovery tank for refrigerant, and equipment to charge the system. The advantage of doing it yourself is that you save yourself some money.

To begin, turn the air conditioner off, disconnect the power cord from the wall outlet, and turn off the circuit breaker. Next, remove the refrigerant in the system into the recovery tank. Doing this will reduce the pressure and make replacing the compressor easy. The air conditioner is usually at high pressure to keep the refrigerant circulating.

Now, cut the lines through which refrigerant flows into the compressor. You will need a torch to melt the copper lines before removing the compressor. After cutting the lines, disconnect the electrical connector and unbolt the compressor, lifting it out of the condensing unit.

Put the new compressor in the place of the old one and bolt it in place. Connect the electrical connector and braze the copper lines to the compressor using the torch. Then, put the outside condenser unit together and charge the system with refrigerant you recovered or with fresh ones.

Can an Air Conditioner Compressor Be Repaired?

An air conditioner compressor cannot be repaired once it is broken. The only fix for a broken or damaged air conditioner compressor is a total replacement. If it stops running, you can reset the compressor by turning the thermostat off, unplugging the unit for about a minute, plugging it back, and turning on the thermostat. Then, set the temperature on the thermostat and allow the compressor to turn on and run. If that does not happen, it may be damaged; consider replacing it.

Can an Air Conditioner Compressor Explode?

The compressor of an air conditioner can explode. Although it is not a common occurrence, there have been cases of compressor explosions while HVAC technicians were fixing them, and three of these explosions resulted in death. It may have resulted from built-up pressure within the compressor or overheating, among other possible causes.

Does an Air Conditioner Compressor Need to Be Level?

The compressor of an air conditioner needs to be as level as possible. An almost-unnoticeable slant may not affect the compressor a lot, but if it noticeably slants, the compressor may malfunction and wear out too quickly.

Most manufacturers recommend placing the condenser unit on a concrete slab which you can buy from hardware stores. You should also put rubber pads on the concrete before setting the condenser on the concrete to cushion the movements. However, all these must be level for the refrigerant to flow smoothly from the compressor into the unit and back.

If your condensing unit is not level, put rubber pads that are half an inch thick and place them under the condenser. Rubber mats may also work, but cut them into smaller pieces for the best results. Pay attention to the refrigerant lines and other cables to avoid damaging them. You may want to have someone watch them while you level the outside unit or hire a professional to do the job.

Air Conditioner Compressor and Fan Not Turning On – Solution

The condensing unit may not be getting power if you find that an air conditioner compressor and fan are not running simultaneously. Check the circuit breaker beside the condensing unit to see if it is tripped.

If the breaker is tripped, turn the thermostat off and reset the breaker. Next, turn the thermostat on and set the temperature. Ensure you set it to a temperature a few degrees lower than the room temperature; it must be cold enough. Then, turn on the air conditioner and see if the fan and compressor start running.

If they still do not run, you may want to check the compressor contactor. The part supplies power to the compressor and fan motor, and if it becomes faulty, both parts will not work. Hire an HVAC technician to test the contactor and see if it is causing the problem. If it is, the technician is in the best position to replace it.

You may also want to check the capacitors that supply power to the compressor and fan motor. If they are defective, the fan and compressor will not work. At first glance, it may be evident whether or not the capacitors are faulty. They may be bulging or leaking fluid, corroded or rusted, and these are clear signs that you should replace them.

However, if it is not immediately evident that they need a replacement, run a continuity test using a multimeter. If either or both capacitors show no continuity, replace them. And if you cannot fix the issue yourself, let a professional technician do the job. It is always best to use the services of an HVAC technician when you need to repair or service your air conditioner.

Air Conditioner Compressor Blowing Cold Air – What to Do

Check the air filter if you find that your air conditioner compressor or condenser is blowing cold air. When it becomes dirty with dust mites and other air pollutants, it will restrict the flow of air in and out of the unit. 

Remove the filter, place it under running water, add a little mild soap, and thoroughly wash it. Afterward, dry it with a lint-free cloth and leave it out to air-dry completely before putting it back into the air conditioner.

If the filter is not the cause of the problem, check the thermostat. It may be malfunctioning and switching from cooling to heating mode. The condenser will blow cold air when this happens, while the indoor unit will blow hot air. Ensure it is set to cool and adjust the temperature low enough. Allow the unit to run for a couple of hours to see if the issue resolves.

If it does not, it may be a wiring problem. It is a straightforward fix, and you may not need a new thermostat. If you do not know how to fix the wires, let a professional do the job. But if the problem continues, you may have to replace the thermostat.

Another possible cause of a compressor blowing cold air is low refrigerant level. Overuse of the air conditioner can lead to a drop in the level. The same is true if there is a leak in the closed system. However, you cannot fix this problem yourself unless you are trained and licensed. Hire a certified technician to check and repair leaks and recharge the system if necessary.

The technician should also check for correct wiring after refilling the refrigerant if the problem continues after that. Wrong connections or disconnected wires can result in the compressor not functioning correctly. You can also check the wiring yourself if you have the training.

In addition, check the capacitor. A faulty capacitor can affect the functionality of the compressor. While checking the capacitor, test the compressor because it may be the source of the problem. Hire a technician to check both parts, and if the compressor is the problem, the technician will recommend the best solution.

Air Conditioner Compressor Bearing Noise – Quick Fix

Running a test on your air conditioner’s compressor is the best way to determine whether or not the bearing is noisy. If it is, it means the compressor is failing due to age. You may need a new compressor. A repair may not work and if replacing the compressor is expensive, consider investing in a new unit.

Air Conditioner Compressor Does Not Turn Off – How to Fix

Check the following if an air conditioner compressor keeps running without turning off:

1. Thermostat

Setting the thermostat too low will keep the compressor up and running. The thermostat’s job is to inform the air conditioner of the correct temperature it needs to reach. Try adjusting the temperature setting on the thermostat to a warmer setting and see if the compressor turns off.

If it continues running, it may be because the thermostat is defective. Due to age, its connection to the outdoor condensing unit may be disconnected or weak. This may result in the thermostat misinforming the compressor and keeping it running all the time. Consider replacing the thermostat if that is the case.

2. Filter

Ensure the air filter in the air conditioner is clean and still suitable for use. You can open or remove the front panel to inspect the filter; the method will depend on the type of air conditioner you own. Clean it with a brush or wash it in warm soapy water. Put it back into the air conditioner when it is completely dry. But if it is old, replace it entirely.

A dirty or old filter will cause dirt to clog the system, and when this happens, the unit will freeze. Consequently, there will be a reduction in cold air, which triggers the compressor to keep running to make up for it.

3. Condenser Coil

Like the air filter, the condenser needs to be clean for the air conditioner to function well. Open the condensing unit outside the house and inspect the fins. If they are dirty, wipe them using a small brush attached to a vacuum cleaner. You can also wash off clinging dirt with a hose if necessary, but you must not be forceful.

If the condenser is dirty, it will trap heat within the system and reduce the cooling capacity. Over time, the compressor will run more than it should to help the unit maintain a cool temperature. The risk is that compressor may wear out prematurely.

4. Refrigerant

Low refrigerant in the sealed system can lead to the compressor not turning off. The air conditioner needs refrigerant to produce cool air, but when there is not enough left in the system, either due to a leak or overuse, there will not be enough cold air due to a leak or overuse. As a result, the compressor will run non-stop to keep the room cool. Therefore, check for leaks and repair them before adding refrigerant. You may need the help of a service technician if you do not have the certification or training to recharge an air conditioner.

5. Compressor Contactor

When the contactor of the compressor closes, it allows electric power to flow to the compressor and fan motor. Only a technician can determine whether or not the contactor is faulty and replace it.

Typically, a 24-volt current flows to the contactor, and it closes so that the fan and compressor can run. But when the air conditioner achieves the set temperature, the contactor needs to open so that the cooling system can stop running. However, if the contactor remains closed due to a malfunction, the compressor will keep running.

6. Thermistor

The temperature sensor or thermistor needs to be in good working condition to inform the control board of the temperature needs. If the thermistor is not working, the control board may keep the cooling system up and running all the time, even when the temperature is cold enough. 

The air conditioner’s specification sheet has the resistance values for all the components of the unit so that you will find the resistance value for the thermistor in it. Use a multimeter and check the thermistor; replace it if its resistance value does not match the specification sheet.

Clean and run maintenance checks on the air conditioner so that it runs as it should. Doing this will eliminate minor faults that may eventually become serious. If none of the above steps fixes the problem or you are unsure of how to troubleshoot the unit, get a professional technician for the task.

Air Conditioner Compressor Delay – What It Means

Newer model air conditioners generally need about five minutes for the pressure to equalize. Usually, the pressure in the condenser and the evaporator during the cooling process is different. Both the high and low pressure must equalize before the compressor can start, which may take up to five minutes. The unit may lock up and blow a fuse if the compressor tries to start without releasing the pressure.

Air Conditioner Compressor Fan Not Running – Solved

If the compressor fan of an air conditioner is not running, check the following:

1. Contactor

The contactor is a switch that sends power to both the fan motor and the compressor. If it becomes faulty or stops working, the fan may not work. You will need the services of a technician to test the contactor and if it is faulty, replace it.

2. Fan Motor

The problem may stem from a defective fan motor. Turn the blades to see how well they turn. If they are stiff, it may indicate that the motor bearings are worn. If that is the case, replace the motor because you cannot repair the worn bearings. But if bearings are not worn yet, the fan does not run, get a multimeter and check the motor for continuity. Replace it if there is no continuity.

3. Capacitor

You will see a small cylindrical component with wires connecting to the fan. It is the capacitor. With constant use, the capacitor can wear out. It may also get damaged, which is evident if it is rusted, corroded, leaking, or bulging at the top. Replace it if you notice any of these. But if not, run a continuity test on the capacitor and replace it if you find no continuity.

4. Fan Belt

Some older air conditioner models use fan belts. The fan motor will stop running if the belt slips off or snaps. Examine the belt to determine whether or not it needs repairing. Consider using the services of a technician for the best results.

Air Conditioner Compressor Kicks On and Off – Solution

If you find that your air conditioner compressor kicks on and off in short intervals, check the following:

1. Thermostat

A faulty thermostat will turn the air conditioner compressor on and off because it determines when the cooling system runs. Ensure the wiring is correct and not disconnected. Also, ensure the thermostat is in good working condition and if it is not, replace it.

2. Run Capacitor

The run capacitor provides the power that the compressor needs to run until it stabilizes. It requires a lot of electric power to start and run, so if the capacitor is defective, the compressor will turn on and off within short periods.

Ensure the capacitor is fully connected to the compressor and is not bulging or leaking. Also, check to see if it has continuity. If the capacitor has no continuity, it cannot provide adequate power for the compressor to run. Since you cannot repair a defective capacitor, the only solution is to replace it.

3. Filter

It is crucial to check the filters in your air conditioners and clean them every month. In some cases, it is necessary to clean them every two weeks. Filters have the job of removing pollutants from the air, and considering the state of the Earth, there are many pollutants to filter. 

Therefore, the air filter tends to get dirty pretty quickly. If you do not clean or replace the filter when due, dirt will clog the system and restrict the flow of cold air. As a result, the compressor will run to make up for the air loss and eventually start overheating. This will lead to the compressor shutting off and turning off too frequently. 

4. Condenser Coil

Inspect the coil and clean it with a vacuum with a brush attachment. Do a thorough job of cleaning it to remove debris. If necessary, wash it with water for better results. Cleaning the coil is a delicate job and may be best if it is done by a professional. If you damage the fins while cleaning them, you will need another unit. 

If the coil is significantly dirty, the compressor will overheat and shut itself off as a protective measure. It may turn back on when it cools but will go off again if it starts overheating. Also, the air conditioner will be unable to produce cool air because the dirty condenser cannot release the heat from the refrigerant. It will remain trapped in the system and reduce its cooling capacity.

5. Refrigerant

Too much or too little refrigerant will affect the compressor. When the refrigerant is too much, the liquid form may flow into the compressor and cause a malfunction. And when it is too little, the compressor will run too long, overwork itself, and begin to malfunction. If it is a refrigerant problem, you will need an HVAC technician for further assistance.

6. Evaporator Coil

Always keep the air filter clean to avoid issues in the air conditioner. Dirt on the filter will directly affect the evaporator coil, and it will trap the cool air and cause the coil to freeze. And when the coil freezes, it cannot release cold air, reducing the production from the air conditioner. 

Consequently, the compressor will run non-stop to cover the slack and over in the process. Overheating causes the compressor to shut down; it will turn on again but may go off if it continues overheating.

7. Size

An oversized air conditioner will quickly cool the room and turn off. While it may sound like saving money on electricity bills, it may also mean that the short running time does not rid the air of humidity. 

If that happens, the humidity will leave areas of heat that will cause the compressor to turn on again too quickly. This process will continue as long as you have an oversized air conditioner. Consider investing in a new unit or getting an outdoor condensing unit that matches the indoor unit.

In addition to the above, check wire connections, especially those going to the compressor. There may be loose connections, frayed wires, or weak ones. Have the manufacturer service your air conditioner or hire an independent but qualified technician.

Air Conditioner Compressor Dripping Water – Quick Fix

An air conditioner compressor will only drip water if the drain line is clogged or the drain pan is damaged. The water will overflow and drip onto the condenser outside, then slide off the compressor and other components to the floor. It does not originate from the compressor because it does not handle water.

In light of the above, check the condensate drain line if you see water dripping from the compressor. Note that a bit of water from the drainpipe outside is nothing to worry about because the air conditioning process produces water. But if the water is excessive and pools constantly, the drain line may be blocked.

Turn the air conditioner off and check the drain line. If you notice debris, use a wet/dry vacuum to clear the line; you can rent from a hardware store if you do not own one. Another option is to use a solution of water and vinegar or bleach; it will wash the dirt out of the drain line.

If the pan is cracked, you will need a new one. Otherwise, condensate will keep draining out and flowing over the condenser. Over time, it will cause problems in the unit and may even lead to mold growth within and outside the house.

The evaporator coil may be frozen, and if it is, it will explain the water constantly dripping from the unit. Turn the cooling mode off and disconnect power from the air conditioner. Allow it to sit unplugged until the evaporator coil thaws. Another option is to use the Fan mode to blow warm air over the coil until the ice melts.

Afterward, check the air filter and clean it if it is dirty. It is one of the primary causes of a frozen evaporator coil. Another thing to check is the refrigerant; an insufficient amount will cause the coil to freeze.

Air Conditioner Compressor Frozen – Quick Fix

A significantly dirty air filter can cause issues with an air conditioner, including a frozen compressor. If you find that your compressor has a block of ice covering it, check the air filter. Open the front panel of your air conditioner and inspect it. If it is dirty or you have never cleaned it, remove it, put it in warm soapy water, and wash it. And if it is due for a change, get a replacement.

While checking the filter, it is also crucial to check the evaporator coil. If it is dirty or frozen, it will restrict the flow of cold air and build it until it reaches the outside unit. This may take some time, but it eventually happens. Clean the coil if it is dirty or turn the unit off to allow it to thaw if it is frozen.

Furthermore, the expansion valve that connects to the compressor may be broken. A broken valve cannot control the amount of refrigerant that flows into the cooling lines. As a result, the compressor and other components will freeze. Use the services of an HVAC technician to fix the expansion if it is broken.

Too little or too much refrigerant in the system can cause the compressor to malfunction or freeze. You may not be able to tell if the refrigerant is the correct amount, so hire a technician to determine the gas level in the system and offer further assistance.

In addition, clean the condensate drain line to prevent water dripping around the compressor and freezing. Also, ensure the drain pan is not overflowing or leaking. Water leakage causes several issues with an air conditioner apart from the compressor freezing.

Air Conditioner Compressor Getting Hot – What to Do

A defective condenser fan, dirty condenser coil, refrigerant issues, voltage spikes, or a heat source causes the compressor to overheat. Your first stop should be the condenser fan. Check the blades to see if anything is caught in them. Clean them if they are dirty and ensure they are not obstructed.

If the blades are free without the fan running, check its capacitor. Replace it if it is leaking, rusted, bulging, or corroded. Do the same if the capacitor has no continuity. And if the capacitor is not the problem, check the fan motor. Replace it if it is no longer working.

Next, check the condenser coil and follow the cleaning instructions in the manual to clean it if it is dirty. A dirty coil will cause the compressor to overheat and may even lead to the condenser fan not working. This is because the heat transfer from the air conditioner to the outside air does not happen, causing it to remain trapped. The cooling capacity drops, and the compressor works extra hard, which means it overheats.

The refrigerant may be too much in the system and may be causing the problem if cleaning the condenser and fixing the fan does not work. Too much refrigerant can adversely affect the compressor like too little refrigerant can. So, you may want to hire an HVAC technician to check the system to determine whether or not to reduce the refrigerant.

If there was a recent power outage, the compressor might be overheating due to a voltage spike or power surge. Ensure the circuit breaker has not blown a fuse; hire an electrician to check the wiring and fuses. Also, ensure the compressor is getting enough power because it may overheat while trying to run if it is not.

Furthermore, check to see if the compressor is short-cycling. If it is, it will explain why it is overheating. A compressor will short-cycle if the condenser is dirty, the filter is dusty, the capacitor or thermostat is defective. You should also check to see if the evaporator is frozen, the refrigerant is too much or too little, or the air conditioner is too big for the room.

Additionally, the compressor will overheat if a dryer vent or another heat source is close to it. The same applies if sunlight is directly hitting it. While you may not be able to do much about the sunlight, you can shield the unit from the glare. The same applies to other heat sources. You may have to consult with a technician to find the best way to protect the compressor.

Air Conditioner Compressor Gas Leak – What to Do

If you suspect or are sure your air conditioner is leaking gas, the first step is to turn off the air conditioner. Disconnect it from electric power and leave it unplugged. The next step is to open windows and doors to encourage cross-ventilation of air. It will blow the gas out of the room and eliminate the risk of poisoning.

Then, call an HVAC technician to check the air conditioner. It may have holes in the closed system, which is the most probable reason for a gas leak. The technician can detect the leaks, patch them, and check the amount of refrigerant lost. That way, they can recharge the system. A gas leak can damage the air conditioner if it is not quickly fixed.

An air conditioner gas leak can cause nausea, dizziness, headaches, and possibly asphyxiation. Since refrigerant is hardly detectable because it is usually odorless, you may not detect it on time. So, you may want to check yourself and any other person in the house for possible poisoning.

Air Conditioner Humming – Solved

Typically, an air conditioner hums when it starts and runs. The hum is low and quiet and does not interrupt the conversation. But if it becomes too loud, there may be a problem with the compressor. And if it is humming without starting, you may want to check the capacitor, fan motor, or thermostat.

You may want to run a maintenance check on the air conditioner once a month or every two months. It will ensure you catch problems before they damage the air conditioner. Get a professional HVAC technician to check the unit and fix any issues.

Air Conditioner Compressor Is Loud – How to Fix

The compressor of an air conditioner can make different loud noises, and the following are ways to fix such noises:

1. Rattling Noise

The compressor may be rattling because it is sitting on loose springs, or the refrigerant may be too high in the system. There may also be loose internal tubes or other loose parts. Whatever is causing the compressor to rattle needs the attention of an HVAC professional.

2. Banging Noise

The piston pin may be dislodged, or the crankshaft may be loose. If that is the case, the parts will hit the sides of the compressor housing, creating banging noise. The compressor will need to be replaced if none of the parts are loose and nothing else seems to be causing the noise.

3. Buzzing or Humming Noise

A compressor makes a humming noise when it operates normally. But if it begins to hum loudly or buzz, check the fan blades and motor. Ensure the blades are aligned, and the motor is in good working condition. The problem may also stem from a faulty electrical component or disconnected wiring. Fix these possible causes and try the compressor again. If the noise continues, you will need the help of a professional.

4. Clicking Noise

Check the start relay to ensure it is working. Test it with a multimeter to check for continuity. If there is no continuity, replace the relay. Also, the fan motor can cause this noise, and while checking the motor, ensure the compressor capacitor is not damaged. Clean the fan motor and test it along with the capacitor. Replace them if they are defective. In addition, examine parts to ensure none is loose. Tighten those you can or call for professional help.

5. Hissing Noise

There may be debris causing an internal blockage. If that is the case, check the areas around the compressor to ensure nothing is entangled there. Also, hissing noise may be because the compressor has high pressure. You should turn the air conditioner off immediately you hear a hissing noise from the compressor. Then, call for professional assistance.

6. High-pitched Noise

Such noise may stem from a failing compressor. It may sound like a squeal, scream, or screech, and it is an indication that you need a new compressor. The noise may also be due to built-up pressure in the compressor or a failed motor. Turn the air conditioner off, allow it to sit for a minute, and turn it on again. If the noise persists, hire a qualified technician to diagnose the problem and fix it.

Air Conditioner Compressor Keeps Running When Turned Off – Solutions

Check the thermistor, temperature control thermostat, and the electronic control board of the air conditioner if it keeps running when it is turned off. The relay switch of the thermostat, also known as the dial, maybe stuck, causing the compressor to stay up and running after the room temperature reaches the set point. You may need to replace the thermostat if you cannot fix them.

Next, test the thermistor. It is a sensor connected to the control board to detect the air temperature and relay the readings to the board. It works with the thermostat to keep the air conditioner running when it should. Run a continuity test on the thermistor using a multimeter and replace it if there is no continuity.

There is a chance that your air conditioner is smaller than the room where it is installed. Air conditioners are measured by British Thermal Units (BTUs) to determine what capacity fits a space by square footage. If the unit has a capacity too low to cool the room because of the size, the compressor will keep running as the thermostat senses that the room is not cool enough. You may have to purchase a bigger air conditioner if that is the problem.

Lastly, check the control board if the thermostat and thermistor are in good working condition. A faulty PCB will keep the compressor and other parts of the cooling system running even after the room becomes cold enough. If every other component checks out, consider replacing the control board.

Call for professional HVAC assistance if the air conditioner keeps running when turned off, even after fixing the above issues.

Air Conditioner Compressor Leaking Oil – Fixed

Check to see if the oil originates from the compressor. Sometimes, the engine leaks a bit of oil, which may flow on seams, reach the compressor, and drip from it. You will find the engine above the compressor. If it has no signs of leaking oil, thoroughly inspect the compressor for a leak. If the oil comes from the compressor, it may have a failed seal. The only solution is to replace the compressor.

Air Conditioner Compressor Locked Up – Solved

You can use the help of an HVAC technician to free the compressor if it is locked up. But it may run only for a short period before locking up again. It may also run for a while and serve you before you have issues with it again. How the compressor responds when you free it will depend on how well you have maintained the air conditioner.

A hard start kit may get your compressor free and keep it running for a long time. The kit provides an extra power boost to jerk it back to life. However, if you need the equipment to start and run your air conditioner’s compressor, it indicates that the compressor is nearing its life’s end.

When an air conditioner is exposed to excess moisture or experiences voltage spikes, it may lock up due to damage. A few other things can cause an air conditioner compressor degradation, but when this happens and emergency kits and efforts do not solve the problem, consider replacing the compressor or the entire air conditioning unit. Get different opinions before making a decision.

Air Conditioner Compressor Life Expectancy

A typical air conditioner compressor has a life expectancy of ten years, and some last longer than that and reach fifteen years. The air conditioning system may last up to twenty years. However, a compressor’s life expectancy can extend to longer years if you regularly and adequately maintain the air conditioner. How often you use the unit, the manner of usage, and where you put the outdoor condensing unit also affect the lifespan of the compressor.

Air Conditioner Compressor Makes Loud Noise When Starting – Fixed

The compressor motor may fail, and the noise is alerting you. One way to tell that the compressor is not optimally working is if there is a reduction in cold airflow. If the air conditioner comes with a damper, it may be causing the noise. The damper controls the amount of cold air in different parts of a house, which means it is a central air conditioner. It may be the damper kicking into action when the air conditioner starts.

The fan may also be causing the noise as the air conditioner starts, or the blower in the indoor unit may be banging against the housing. Whatever the case may be, it is best to contact a certified HVAC technician to diagnose the problem. You can also contact the manufacturer for the same purpose, especially if you still have an active warranty.

Signs of an Air Conditioner Compressor Failure

The following are signs your air conditioner compressor is failing:

If your compressor starts leaking fluid, whether it is liquid refrigerant or oil, it may be that the seals have weakened or the bearings are loose. You may hear loud noises coming from the compressor due to loose parts, and the air conditioner will no longer function as it should.

Another sign is loud noises. Typically, an air conditioner compressor hums but is always quiet. If the hum becomes excessively loud or turns into a buzz, it is a sign the compressor is failing. You may also notice that the compressor has a more challenging time starting or shutting off. And other noises may accompany the failure the longer you use the air conditioner.

A reduction in airflow from the air conditioner is one problem that should lead you to the compressor. The more you use the unit, the more the airflow decreases. It could be several other problems, but it is good to check the compressor while troubleshooting other parts.

In the same vein, warmer air from the air conditioner may point to a faulty compressor. If your unit is the heating and cooling model, ensure it is set to Cool; the indoor unit will blow only warm air if it is in Heat mode. But if it is set to Cool and blows warm air, use the eliminating method to narrow the possible causes. If you arrive at the compressor, it is failing.

Furthermore, overheating may be one way to damage a compressor. A dirty filter, frozen coil, dirty condenser, defective fan, or power surges can lead to a hot compressor. However, wear and tear can also cause the compressor to overheat.

Finally, check your electricity bills. If there is a recent spike that coincides with the compressor problems, it may indicate that the compressor is drawing more energy due to an inability to function normally. The best step is to contact the air conditioner manufacturer or use the services of a certified HVAC technician.

Air Conditioner Compressor On But Not Cooling – How to Fix

There are a few other things that lead to an air conditioner not cooling, even when the compressor is on:

1. Dirty Air Filter

Cleaning the air filter in your air conditioner is one of the most straightforward tasks. Open the front grille or lift the filter’s handle up and out. Put it in a sink or container and wash it with warm soapy water. Afterward, flick it to dry and ensure it is completely dry before putting it back into the indoor unit.

A dirty filter restricts the airflow and reduces the air conditioner’s cooling capacity. The filter can stop the air conditioner entirely from working in severe cases.

2. Faulty Thermostat

Ensure the operation mode on the thermostat is set to Cool. if it is not, adjust it accordingly. But if it is and the house is not cooling with the air conditioner running, ensure the temperature setting is a few degrees lower than the room temperature. Make the necessary adjustments and wait for changes.

If there is no positive change, the thermostat may be faulty. Loose wires and faulty components can affect how well it functions. You can either let a technician fix it or replace the thermostat.

3. Evaporator Coil

When a filter in an air conditioner gets significantly dirty, it affects the evaporator coil. The dirt traps the cold air in the coil and leads to freezing. And if the evaporator coil is frozen, there will be no cold air from the air conditioner.

Inspect the evaporator coil; you will find it behind the air filter in most units. If it is frozen, you can use the Fan mode of operation to blow warm air over it to melt the ice. Alternatively, turn the air conditioner off until the ice melts off the coil. Check possible causes of a frozen evaporator coil and fix them.

4. Condenser Coil

With constant use, dust and debris can clog the condenser and prevent the effective dissipation of heat from the air conditioning system. Therefore, it is crucial to the efficient running of the unit that the condenser is unclogged and clean. Otherwise, it will block airflow into the unit and trap heat to reduce the cooling efficiency. If you are unsure how to clean the condenser, contact an HVAC servicing company.

5. Small Unit

An air conditioner’s capacity is measured based on the amount of cool air it can provide in a room as measured in British Thermal Units per Hour (BTUh). It may not be an issue if the weather is normal, but when it gets hot, you will notice that the air conditioner cannot cool the room well.

The construction quality of the house, square footage, the weather in the area, and insulation are some factors that determine the functionality of an air conditioner. If you are unsure of the size of your home or the capacity of the air conditioner, you can request professional help. Then, you can decide whether to get a bigger unit or use a ductless unit to support the air conditioner.

6. Sealed System Leak

If the air conditioner has a leak in the sealed system, it will lose refrigerant. And if that happens, the compressor may be running but the air conditioner will not produce cool air. The refrigerant is what absorbs the heat from the room air, leaving it cool. Without enough refrigerant in the closed system, the air conditioner cannot work as it should.

If there is a suspected leak, only a technician can detect and fix it. It is important to find the leak before recharging the system; adding refrigerant to a leaking system will only lead to more leaks and endanger your health.

It may be ideal to use the services of a professional to find out why an air conditioner compressor is on but the unit does not produce cold air. If there is an underlying electrical issue, they are in the best position to find and repair it.

Air Conditioner Compressor Shaking – Quick Fix

The compressor may be unbalanced. There are springs or screws that hold the compressor secure to the housing, and if the screws come loose, the compressor will shake or vibrate. You will notice it whenever the air conditioner cycles on and off.

The shaking may also stem from a mechanical fault in the compressor. Get the help of a certified technician to determine why the compressor is shaking. Also, if it needs a repair, the technician can do the job or replace the compressor if necessary.

Air Conditioner Compressor Tripping Breaker – Quick Fix

If the compressor of your air conditioner is tripping the circuit breaker, there may be an electrical issue. Power surges cause the breaker to trip and a faulty component such as a capacitor can lead to the problem. Also, check for loose connections or shorts in the wiring. Let a professional technician check the air conditioner compressor and other connecting parts to see if there are faults.

Can an AC Compressor Cause Engine Problems?

A faulty air conditioner compressor can affect the engine of your car if you do not fix it. A car air conditioner runs on the power of the engine and if the compressor fails, the engine will stall due to defaults in the pulley bearings. Besides that, the belt may break and affect all the other accessories it moves. A car technician can check the compressor and whether or not it is faulty and affecting the engine. Then, they can recommend a permanent solution.

Air Conditioner Compressor Not Working After Power Outage – What to Do

Reset the air conditioner and see if the compressor starts working again. Turn off the thermostat and disconnect the air conditioner from the wall outlet. Next, turn off the breaker that controls the air conditioner and turn it on again. Now, give the air conditioner thirty minutes to allow the internal breaker to reset.

Ensure the thermostat remains off all this time. If you turn on the thermostat and the air conditioner starts cooling, the compressor will not reset. When the time elapses, connect the air conditioner to electric power, turn on the thermostat, and set it to Cool. If the compressor does not start working, the issue may be more serious and will need a technician to fix it.

Difference Between an Air Conditioner Compressor and Condenser

The primary difference between the compressor and condenser of an air conditioner is in what they do. A compressor prepares the refrigerant by pressing it flat for when it gets to the condenser. The job of the condenser, on the other hand, is to change the refrigerant from gas to liquid-vapor. It is in this form that it flows to the necessary parts of the unit for the cooling process.

Both parts also do not look alike. A compressor is a small round device while the condenser looks like fins. The difference in their appearance is another marked difference between the compressor and condenser.

What Are the Three Most Common Types of Air Conditioner Compressor?

The three most common types of air conditioner compressors are centrifugal, rotary screw, and reciprocating compressors. A centrifugal compressor works by an energy transfer from a rotating impeller into the air. Such a compressor does not need oil to run.

The rotary screw compressor has two rotors in a casing that internally compress the air. It has no valves and is cooled by oil that seals the clearances inside it. A reciprocating compressor reduces the volume of air and increases the pressure, and it uses a piston to work.

Can You Bypass an Air Conditioner Compressor?

You cannot bypass the compressor of an air conditioner unless you use a bypass pulley. If you can remove the pulley bearing of the ol and damaged compressor, buy a new one and install it. Then, use a serpentine belt to finish the job. Sometimes, it is more expensive to install a bypass pulley than to replace the damaged compressor. So, get a professional opinion about whether or not it is best to use a bypass or get a new compressor.

This video demonstrates how to bypass an air conditioner compressor using a bypass pulley…

How to Clean an Air Conditioner Compressor

Cleaning the compressor of an air conditioner means cleaning the condensing unit. You will need to carefully wipe dirt and dust off the compressor; do not pour or spray water over it if you do not have to because it may get damaged. Cleaning with a vacuum brush attachment may also work to remove dust and debris. The best idea is to use the services of a professional technician if the compressor needs a thorough cleaning.


There are many things that can go wrong with an air conditioner compressor. It may stop working, become noisy, shake or vibrate, freeze, run without cooling, and other issues. Fortunately, most of these problems have solutions, and this article is a detailed guide on fixing them. Also, you find some of your compressor questions answered in the article.

If you have serious compressor problems, it is best not to try fixing them yourself. This is especially true if you have no training for such jobs or the compressor is still usable. Attempting to fix it yourself may irreparably damage the unit. Instead, contact the manufacturer, report the compressor issue, and request service. Alternatively, hire an independent technician to troubleshoot the air conditioner and fix the issues.

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