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AC Capacitor Has Been Replaced But Still Not Working: Why And How To Deal With It?

AC Capacitor Has Been Replaced But Still Not Working: Why And How To Deal With It?

AC capacitors play a crucial role in the functioning of an AC unit. When they fail, the entire system can come to a halt. If you recently replaced your AC capacitor with a brand new one but are still facing issues, it’s essential to understand the underlying problems and find effective solutions. Our extensive research has uncovered the most common causes behind this problem. In this article, we will provide you with valuable tips to help you troubleshoot and resolve these issues.

There are several reasons why a newly installed AC capacitor may not work as expected, and each has its own corresponding solution. Let’s explore some of the potential causes:

Incorrect Voltage Rating

The voltage rating indicates the amount of electricity an AC capacitor can handle without sustaining damage. AC capacitors come in various types, each with a different voltage rating. It is not uncommon for technicians to mistakenly choose a capacitor with the wrong voltage rating. Even if you have recently replaced the capacitor, if the new one has an improper voltage rating, it can malfunction and pose safety risks. Furthermore, using a capacitor with an incorrect voltage rating for your AC unit can significantly reduce its lifespan, leading to frequent repairs or the need for another replacement.

To address this issue, you should compare the voltage ratings of the old and replacement capacitors after disconnecting and discharging the old one. While the microfarad (F) value should match, the voltage rating does not necessarily have to be the same as the existing capacitor. However, the voltage rating should be at least 1.5 times or twice the highest voltage it will encounter. It is crucial to ensure compatibility with voltage, physical dimensions, and lead spacing as well. Using a multimeter, you can measure the voltage rating of the capacitor to confirm if it is functioning within the required parameters. The tolerance information can usually be found on the capacitor data tag.

Damaged Parts

Even with a new and correctly rated capacitor, other faulty components in the AC system can cause the capacitor to fail. It is essential to inspect the entire AC unit to identify any potential issues. A damaged bearing in the compressor or fan motor, for example, can lead to the failure of a newly installed capacitor. Unusual noises during the operation of the fan or restricted airflow due to debris can be indications of a faulty fan motor.

To address this problem, conduct a thorough examination of the motor and the power supply to the air conditioner. Ensure that the compressor is receiving the correct amount of power and that the circuit breaker has not tripped. Additionally, inspect the fan motor windings for any shorts or openings, which can be determined by measuring the ohms. A zero reading indicates a short in the fan motor winding, while a perpetual reading suggests an open motor winding. In both cases, the fan motor would need to be replaced. It is also essential to check the wiring and connections for any signs of damage.

Overheating AC Capacitor

AC Capacitor Has Been Replaced But Still Not Working: Why And How To Deal With It?

Excessive heat can negatively affect the performance of an AC capacitor, even if it has been recently replaced. When the electrolytic AC capacitor becomes too hot, the wet separator within it can dry up, leading to an internal short circuit. Regularly exposing capacitors to temperatures above 150 degrees Fahrenheit can cause them to malfunction. Overheating can occur when the relay switch malfunctions, causing the capacitor to remain in the circuit for an extended period. Moreover, the combination of intense sunlight and prolonged operation of the AC unit on hot days can contribute to overheating, reducing the capacitor’s power efficiency and lifespan.

To mitigate this issue, it is crucial to check the AC unit and capacitor on hot days. Avoid direct sunlight exposure by providing shade or using appropriate covers for the unit. In many cases, c

logged or dirty condensate coils can cause AC capacitors to fail due to increased power demand from the compressor and fan. Regularly inspect and clean the condensate coil in the outdoor unit to prevent debris accumulation. Additionally, consider replacing the relay switch if you have an older AC system.

Power Surge And Electrical Overload

Although rare, power surges caused by lightning strikes during storms can damage AC capacitors. Mild power surges resulting from power grid oscillations can also harm the capacitors. It is crucial for the compressor and fan motors to reach about 3/4 of their operating speed before the capacitor disconnects them. If electricity demand continues during this period or if the motor stops abruptly or burns out, the capacitor can become overcharged or damaged. Strong power surges can render the capacitor ineffective or cause it to fail entirely, necessitating another replacement.

AC Capacitor Has Been Replaced But Still Not Working: Why And How To Deal With It?

To address this problem, consider installing surge protection devices to shield your AC components from damage during power outages or when the power is restored quickly.

Frequently Asked Questions About AC Capacitors

What Wires Connect An AC Capacitor?

An AC capacitor typically has three wires: red, yellow, and white. The red wire represents the power source, the yellow wire controls the fan motor speed, and the white wire represents the neutral side of the circuit. However, it is important to note that the specific wire colors used may vary depending on the motor manufacturer, application, and age of the unit.

How Many Capacitors Are In An AC unit?

The number of capacitors in an AC unit can vary depending on the brand and model. Some AC units may have one dual capacitor, while others may have two single capacitors, depending on the design of the HVAC system.

Are AC Capacitors Interchangeable?

Run capacitors and start capacitors are not interchangeable due to their design differences and specific placement requirements within the AC system. Using start capacitors instead of run capacitors can result in a short circuit and cause fan motors or compressors to stop working.

What Is The Average Lifespan Of An AC Capacitor?

AC Capacitor Has Been Replaced But Still Not Working: Why And How To Deal With It?

On average, an AC capacitor has a lifespan of approximately 10 years. However, the actual lifespan can vary depending on factors such as the type of capacitor and frequency of use. Therefore, it is important to select a suitable AC capacitor for your unit to ensure optimal performance and longevity.


Troubleshooting an AC capacitor replacement that isn’t functioning properly requires careful consideration of various factors. If you are unable to resolve the capacitor problem on your own or are unfamiliar with electrical components, it is highly recommended to seek assistance from a licensed HVAC company. Professional HVAC technicians possess the expertise to accurately diagnose and address issues within the system, ensuring its efficient and reliable operation.

AC Capacitor Has Been Replaced But Still Not Working: Why And How To Deal With It?

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