What is a Capacitor and Why Do They Break on Air Conditioners?

Living in the desert presents many challenges, but none are as difficult to overcome as the intense heat of the summer. Fortunately, modern air conditioners are constructed with just a few parts, which makes them incredibly reliable.

You can count on your AC unit to keep trucking for years with very little maintenance, but if your air conditioner suddenly refuses to start up one day despite your best care, the capacitor is probably to blame. Though small, capacitors play a big role in your air conditioner’s daily functioning.

What is a Capacitor?

A capacitor is a clever device composed of two metal conductors separated by an insulating material. On an air conditioner, they often look like large, cylindrical batteries with two or three posts sticking out of the top.

The main job of capacitors is to store electrons to provide start-up energy for your air conditioner. When electricity runs through them, they build up a charge by swapping electrons between the two conductive plates inside.

Because of their capacitors, air conditioners do a little magic trick every time they start up. Your A/C unit requires a great deal more start-up energy than is available through your home’s wiring, so the capacitor is added to the circuit to give an electrical jumpstart when the system draws power from the electrical grid. Together, these two electrical sources provide the right amount of juice to your air conditioner. The capacitor’s job is over until an air conditioning cycle is complete. Then the compressor must start up again.

Your air conditioner may contain several different capacitors, including the compressor motor run capacitor, the outside fan motor run capacitor, the indoor fan motor run capacitor and the start capacitor. The most common to fail is the compressor motor run capacitor. It has a big job and an even bigger footprint on your AC system since it’s a dual capacitor with three terminals instead of just two.

Why Good Capacitors Go Bad

Capacitors fail often—they do a tough job, and their work takes a toll. A few factors play heavily into the lifespan of AC capacitors, including:

  • Heat exposure. In Phoenix, heat may be one of the most damaging elements for air conditioner capacitors. Unfortunately, exposing these units to high heat for extended periods greatly shortens their lives and can cause significant damage to your unit. Make sure you shade your air conditioner. Keep it clean and the air circulating to maximize your capacitor’s lifespan.
  • Voltage rating. All capacitors have a voltage rating, which informs air conditioner technicians exactly which capacitor matches which air conditioner. Unfortunately, homeowners may try to cut costs by replacing the AC capacitors themselves without understanding how to choose the right one. An undersized capacitor won’t hurt your air conditioner but will significantly shorten the capacitor’s life. If you decide to DIY this job, remember that bigger is better. If your air conditioning system is a 370-volt unit, bumping up to a 400-volt capacitor will ensure you get enough power and that your capacitor comes closer to reaching its maximum life span.
  • Age. Like all things, capacitors have a limited life span. Most are designed to last approximately 20 years, but several factors can cause them to wear out more quickly. Suppose your air conditioner cycles much more rapidly than average. In that case, your capacitor is undersized (as mentioned above) or built from problematic parts, and the estimated life span may be greatly reduced. Fortunately, these parts are relatively inexpensive to have replaced, so even if your capacitor wears out before your air conditioner does, it won’t break the bank.

How to Know If Your AC Needs a New Capacitor

Below are some telltale signs indicating you have a defective AC capacitor and tips on addressing this issue to restore your cooling system’s performance:

  • Your air conditioner is not blowing cold air. Try resetting your system by turning it off and on again. If the issue persists, it may indicate a faulty capacitor or other malfunction requiring professional attention. Contact a qualified technician to diagnose and repair the problem for optimal cooling performance.
  • High energy bills. A defective capacitor can cause your air conditioning unit to work harder than necessary to cool your home, increasing electricity consumption and higher utility costs.
  • Humming noise. If you hear a humming sound or your AC takes minutes to start, you likely have a failing AC capacitor.
  • Your HVAC system is old. Over time, wear and tear can take a toll on your AC unit, leading to performance issues and component failures. Consider contacting a technician to inspect your system and recommend a capacitor replacement if necessary.
  • Your AC will turn off on its own. A problematic capacitor can cause your air conditioning system to cycle on and off repeatedly, disrupting its performance and efficiency.
  • AC won’t turn on immediately or won’t turn on at all. Suppose you’re experiencing long delays or a complete lack of response when powering your air conditioner. In that case, it’s time to have your capacitor inspected and potentially replaced by a professional technician.

How to Manage AC Capacitor Problems

If you have a problem with your AC capacitor, it is recommended that you have a skilled and qualified HVAC professional to diagnose and fix it. However, you can do a few things to manage capacitor issues until a professional arrives.

  • Turn off the power. Before troubleshooting an AC capacitor problem, turn off your unit’s power first to ensure safety from injuries or electrical shocks.
  • Check for any sign of damage. Examine your capacitor and look for any visible signs of bulges or cracks. If you see any damage, ensure you replace the capacitor immediately.
  • Test your capacitor. Use a multimeter to test if the AC capacitor is working accordingly. If it has lost its capacitance, you need to have it replaced.
  • Clean your AC unit. Debris and dust can accumulate on the capacitor, reducing its efficiency and causing damage in the long run. Ensure your unit is cleaned regularly to prevent similar problems.
  • Schedule routine maintenance. Regular maintenance by a skilled HVAC professional can help keep AC capacitor problems at bay. Routine maintenance can also help identify and address issues before they require costly repair or replacement.

Keep Your AC Running with a Healthy Capacitor

A capacitor is a crucial component of your air conditioning system. If you suspect your AC’s capacitor is malfunctioning, having it inspected and replaced as soon as possible is important to prevent further damage and ensure efficient operation.

If your air conditioner is refusing to start, running with little enthusiasm, making weird noises, or just isn’t cooling right, call Precision Air. Our technicians are NATE certified and trained to handle any problem your air conditioner can throw at them. Remember, we don’t charge weekend fees or add trip charges to your bill; we’ll come out when it’s convenient for you. A quick call to 602-349-6922 is all it takes to schedule your appointment, 24 hours a day, seven days a week!

Precision January 14, 2018

Share This Post:

erik - owner


We want to help you learn about about all things air conditioning and heating! Have any questions or want to see us write about something? Give us a call, chat, or email and we'll do our best to help you out.

  • APS Qualified Contractor
  • BBB Accredited Business Logo
  • SRP certified contractor
  • Arizona Healt Pump Council
  • Energy star logo
  • Electric League of Arizona
  • NATE Logo
Testimonials & Reviews

See what our customers have to say

I wanted to make sure my air conditioner was ready for summer. Fernando came out and made sure my unit was tip top. He was friendly, professional and not a sales man. Thanks Fernando!
Testimonials - Brett Walker
Brett Walker
Colin and Andrea were incredibly professional and knowledgeable. They did a great job representing the company. We will definitely contact them again for any HVAC needs that arise.
Testimonials - Jackie Barkenhagen
Jackie Barkenhagen
We woke up in the middle of the nite on memorial day to a hot house. I called precision at 6am and they were here before noon. Simple problem fixed, cool house. I love these guys!
Testimonials - Nick Corso
Nick Corso
Thank you Ray at Precision Air...the compressor on our AC went out last night and the house was HOT. This morning Ray was there to replace the compressor and had us feeling the cool air again in no time. Great customer service...quick response time and friendly from the first call until the repair was completed. Ray even offered to clean the filters! Thank you!!
Testimonials - Jeneen Piche
Jeneen Piche
I’m so glad I called Precision for my annual AC checkup!! Austin was professional, super friendly and answered all my questions. I’ve had more bad experiences with AC companies here in the valley than good ones. Precision Air will have all my hvac business going forward!! Thanks for being a reputable and honest company!!!
Testimonials - Cara Perlman
Cara Perlman
He did a great job; professional and knowledgeable! Kalin is the technician’s name and Precision Air and Plumbing should take a bow for hiring such an invaluable employee!!!
Testimonials - Jeff Stanczak
Jeff Stanczak
Precision Air is a company of integrity. I signed up with them August 1st, 2019 for their AC maintenance plan for 2 years... Someone from their office called me a week ago to set up their yearly maintenance visit. SO GRATEFUL.
Testimonials - Kingsley Evans
Kingsley Evans
Precision Air and Plumbing is a wonderful company to work with! They are very experienced and professional. They have helped us in our home for many years via a/c service and air duct cleaning.
John Andres - Precision Air & Plumbing
Andrew Burkhart
It was time to replace our AC, and so our choice was Precision Air, as we've been with them for over 20 years. Teman & Julian did an excellent job on the installation today, arriving on time.
Testimonials - David Topping
David Topping
Contact Us

Feel free to contact us any time at 602-349-6922 for immediate assistance.

We offer 24 hour emergency service, and would be happy to schedule an appointment for you, or simply answer any questions you may have.

Precision Air & Plumbing - Chandler AZ Map

This field is for validation purposes and should be left unchanged.

Service and Sales


General Information



Apply Online!

Schedule an Appointment 480-680-9740