Air Conditioner Capacitor [Guide, Problems & Solutions]

Many parts of an air conditioner play vital roles, and one of them is the capacitor. This article discusses an air conditioner capacitor, possible problems, and solutions.

Air Conditioner Capacitor Keeps Failing – Quick Fix

If the capacitor of your air conditioner keeps failing, there are several things to check. The condensing unit may be overheating, putting too much pressure on the capacitor to provide electric power. Too much electric current can also cause the capacitor to fail, which occurs when there is a power surge or voltage spike. The compressor can also draw too much current and overload the capacitor.

Debris from outside has a negative impact on the capacitor. Since it is a small component, it is easily damaged; debris hitting the condenser may get to it. The capacitor failure may also stem from age or use. If you frequently use your air conditioner, you may find that you have to replace the capacitor too often, especially if the condensing unit is exposed to heat.

Most capacitors cannot be repaired when they fail. The best fix in such a situation is to replace the component. However, if you do not find a permanent solution to some of the reasons it fails, you may need a new capacitor soon.

Consider using a surge protector to keep your appliance from an overload when there is a voltage spike. Not only will it protect the capacitor, but it will also protect the compressor and other critical air conditioner parts. 

Check if the condensing unit is exposed to too much heat. If a vented dryer is close to it, create a shield for the condenser. A little shade for the unit will go a long way in protecting it from excessive damage. The best step is to employ the services of an HVAC technician to find out why the capacitor keeps failing and fix it.

Can an Air Conditioner Capacitor Kill You?

An air conditioner capacitor can kill you by electrocution. The primary job of a capacitor is to store electric power and provide a boost for the fan or compressor to start and run. Even when you turn the air conditioner off, the capacitor tends to retain some stored electric power for some time. Eventually, it will release it. However, it can kill you if you touch it while still charged. If not, it can cause a severe injury.

Air Conditioner Capacitor Fire

A defective air conditioner capacitor can cause a short circuit. This problem leads to the stored energy in the capacitor leaking and crossing the barrier. As a result, it will cause a heat buildup and damage the capacitor and other components around it. In the process, it may even lead to a fire. It is best to replace the capacitor if you notice problems or have a professional do the job.

Discharging an Air Conditioner Capacitor

Get a pair of safety glasses and put them on before doing this job. You will also need a grounding rod to discharge electric current from the capacitor. Disconnect the air conditioner from electric power at the wall outlet and the breaker.

Take the grounding rod and connect its wire lead to the ground lug screw of the air conditioner green chassis. Next, unscrew the ground lug and connect the lead connector to its bottom, securing the terminal tightly.

Now, take one probe, touch it to one of the capacitor’s terminals, and leave it there for about twenty seconds. Do the same for all the terminals of the capacitor. If you find that the air conditioner has more than one capacitor, there may be three terminals to test.

The next step is to get a screwdriver and hold it by the handle, which is insulated. Never touch the uninsulated part of the screwdriver while running the test. Touch its tip to one terminal of the capacitor while the shaft touches another terminal. If the capacitor is charged, you will see a spark, but that means it will discharge. Repeat the process for all the terminals to ensure the capacitor fully discharges to earth ground.

It is crucial to discharge an air conditioner capacitor if you want to perform repair work on the unit. The capacitor stores a high volume of electric current that does not quickly discharge. The capacitor can store charge for several days or even months after disconnecting the unit for an appliance as big as an air conditioner. It is a safety measure to discharge it before starting any task.

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How to Check an Air Conditioner Capacitor

You will need a voltmeter or multimeter to check whether or not an air conditioner capacitor is working. Place the test probes on the capacitor’s terminals and check for continuity using the specification sheet for the unit. The resistance values in the sheet will tell you if you need a replacement capacitor.

However, there are simpler ways to determine if the capacitor is bad. Check the condenser fan; if it turns while the compressor runs, the capacitor may not be faulty. But if the fan is not turning while the compressor hums, the capacitor may be faulty. 

Take a long stick, thread it through the grate, and gently push the fan blades. If they start spinning and continue doing so, you need a replacement capacitor. It is the job of the capacitor to provide a boost of power for the fan motor to run. If the fan is not defective, the capacitor is causing the fan problem.

Another way to know if your air conditioner needs a new capacitor is by inspecting it. Sometimes, the capacitor leaks fluid or bulges, and it may also show signs of corrosion and rust. You do not need to test the component if it is visibly damaged.

Air Conditioner Capacitor Life Expectancy

The usual life expectancy of an air conditioner capacitor is twenty years. In other words, a capacitor can last as long as the entire air conditioning system if you run regular maintenance checks on the unit. However, overheating from motors or other heat sources, damaged internal parts, electrical overload, and wear can destroy the capacitor before the expiration of its expected lifespan.

It is one thing to purchase a new air conditioner capacitor, which is usually inexpensive. But the cost of professional services to replace the capacitor is entirely different. You may find an HVAC technician charging hundreds of dollars for the job. It may help to know how to replace the capacitor yourself.

How to Replace an Air Conditioner Capacitor – Steps

To replace the capacitor of an air conditioner, take the following steps:

Press the Power button of the air conditioner to turn it off. Disconnect its power cord from the wall outlet if it applies and turn off the circuit breaker. You may want to use a circuit alert device to ensure you have fully disconnected electric power from the unit for safety measures.

Next, find the capacitor in the air conditioner. It is usually a small cylindrical silver-colored device. If it is leaking fluid or bulging, you need to replace it. Follow the steps in the section on discharging the capacitor to remove electric power from the component before touching it. A capacitor usually stores energy for a long time after disconnection from electricity.

Reconfirm that there is no residual power in the work area using the circuit alert device. Next, remove the capacitor by unmounting the screw holding it in place. The next step is to disconnect the wires from the capacitor but make a note where each one goes; take photos if that will help. 

After that, remove the wires using a needle-nosed plier. Gently disconnect them without applying force; you may damage the wires. And when they are out, place the old capacitor aside and put the new one in its place. Retrace your steps to fix the wires, screw the metal holding band in place, and power the unit.

Air Conditioner Capacitor Humming – What to Do

If you hear it humming in the air conditioner condensing unit, replace the capacitor. A humming capacitor has failed, and the air conditioner will not optimally function with a bad capacitor. Hire an HVAC technician to replace the capacitor or follow the steps in this article to do the job yourself.

Testing an Air Conditioner Capacitor with a Multimeter

The first step is to disconnect electric power from the air conditioner. Turn the unit off and flip the circuit breaker. Next, discharge energy from the capacitor using a screwdriver to avoid electric shock. Remove the wires connected to the capacitor before running the test.

Take a multimeter and place the probes on the terminals of the capacitor. Check the reading on the multimeter; it must be within six percent of the capacitor’s rating. If the result on the multimeter is more than six percent lower than the capacitor rating, replace the capacitor.

Set the multimeter to resistance if it is the analog type. Set it to the highest resistance and place its leads on the terminals of the capacitor. The correct reading should go from zero to maximum. Otherwise, it is bad and needs a replacement.

Air Conditioner Capacitor Leaking Oil – Solved

One of the signs that the capacitor of an air conditioner needs a replacement is if it is leaking oil. It is not a common occurrence but if it does, hire a technician to check and replace the capacitor or follow the steps in this article to change the capacitor yourself.

Note: The same applies if you find that the capacitor overheats or is bulging, which means it looks as if it is packed with more material than it can carry. Also, if it rusted, looks brown and worn out, or corroded, replace the capacitor.

Air Conditioner Capacitor Overheating – Quick Fix

When an air conditioner capacitor overheats, it stops working. The best repair is to replace the capacitor to get the air conditioner condenser up and running again. Several factors cause the capacitor to overheat. When there is a power surge, it overloads the capacitor with voltage and heats it.

The same applies if the relay switch malfunctions. And when the capacitor wears out due to age or overuse, it tends to overheat and may stop working. If you are unsure about the safety of replacing the capacitor yourself, it is best to use the services of a qualified HVAC technician.

Air Conditioner Capacitor Not Working – How to Fix

A few factors inform you that the capacitor of your air conditioner is not working. If the capacitor stops working, the air conditioner will stop producing cool air as it should. Apart from other malfunctioning parts, check the capacitor if the AC stops cooling. If it is defective after testing it, replace the capacitor.

As mentioned before, overheating, power surges, voltage overload, dirt, and age cause the capacitor to stop working. But before deciding that the capacitor is bad, check the following:

When the air conditioner stops turning on, it may be due to a bad capacitor. It is the component that supplies electric power to the compressor and fan’s motor. If it fails to provide the needed power boost, the compressor will not start, and the air conditioner will not run.

Also, the capacitor is bad if you press the Power button on the air conditioner and it does not turn on immediately. If the unit labors to turn on or takes a few minutes to power up, check the capacitor and replace it if necessary. The same applies if the air conditioner turns off without help.

Furthermore, the air conditioner may turn on but not blow cool air. Even if it does, it may not blow enough of it. It may result from blocked vents or dirt restricting airflow, but it may also be the fault of a failed capacitor. While checking the possible causes of the problem, consider checking the capacitor.

In addition to the above, be aware that the capacitor is not working if the condensing unit hums. Typically, the compressor quietly hums when it is running. But if the hum increases and is consistent, it may be that the capacitor has failed. The same applies if the compressor has a hard time starting.

A sudden spike in the electricity bills may indicate that the capacitor is no longer working. When the compressor and fan do not have the required electric power to run, the air conditioner will labor harder to operate. As a result, it will consume much more energy than usual, causing an increase in the bills.

Lastly, an old air conditioner will have failing parts, including the capacitor. If your HVAC system is older than 15 years, it may be time to invest in a new one. Replacing the capacitor and other essential parts may keep it running but not for long. And you may have to keep replacing different parts, reducing cost-effectiveness.

Are Air Conditioner Capacitors Polarized?

Air conditioner capacitors are usually not polarized. A capacitor turns the circuit in an air conditioner and can be plugged in any direction. So, if the air conditioner changes direction, the capacitor remains intact.

However, there are capacitors that cannot be used in air conditioners because of their polarity. When an air conditioner changes direction, the capacitor is damaged because it cannot be plugged in either direction. In other words, the polarity does not change with the signal.

Are All Capacitors the Same?

All capacitors are not the same. Capacitors vary by their capacitance and function. Some can carry more charge than others, and start capacitors are different from run capacitors. Also, some capacitors have a dual role: start and run.

What Type of Capacitor Is Used in an Air Conditioner?

A few types of capacitors are used in an air conditioner. One is the start capacitor. Its job is to provide a boost of power for the compressor to start quickly. Without it, the compressor will have difficulty drawing the needed electric current to start. Sometimes, it may draw more than it needs and damage itself. Once the compressor starts, a potential relay disconnects the capacitor from the circuit.

Two is the run capacitor. It has the job of providing the electric current for the compressor to run after it starts. Typically, a compressor requires more power to stay running than starting. So, some air conditioners have both start and run capacitors for powering the motors in the unit. In addition, run capacitors are more commonly seen in furnaces.

The third type of capacitor, more common in newer HVAC systems, is the dual-run capacitor. This type of capacitor can support both the fan motor and compressor, hence the name. It stays up and running as long as the compressor and fan motor are running. It usually comes with three terminals: common, which connects to the compressor contactor; HERM, which connects to the compressor; and fan, which connects to the fan motor.

How Does an Air Conditioner Capacitor Work?

An air conditioner capacitor gathers electric energy and stores it while the unit is running. You can say it works the way a rechargeable battery works; while the appliance is operating, the battery stores energy to boost the appliance when there is no direct supply of electricity.

So, when the unit needs an electric power boost to start or run, the capacitor supplies it from its storage. Then, it begins to store more energy when the air conditioner is smoothly running. Typically, the blower motor, condenser fan motor, and compressor need the capacitor to start and run because they use engines to operate.


An air conditioner cannot fully function without a capacitor, and the component ensures that every moving part has enough electric power to start and run. So, if an air conditioner capacitor fails, it is crucial to find out and fix the problem as quickly as possible.

In this article, you will learn how to diagnose a faulty capacitor, discharge it, and replace it. You will also know what a capacitor does and where to find it on an HVAC system. In addition, you will see how to test the capacitor correctly and how long it should last in the unit, among other things.

Most importantly, it is best to use the services of a qualified HVAC technician to fix capacitor problems in your air conditioners. If you have an active warranty on your product, contact the manufacturer for free service. You should use a professional because capacitors store charge and may be harmful if you do not correctly discharge it before touching it.

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