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

January 14, 2018

Precision | New AC unit

Living in the desert presents a few challenges, but none are so difficult to overcome as the intense, furnace-like heat of the summer. Fortunately, modern air conditioners are constructed with fewer parts, which makes them incredibly reliable. You can count on your unit to keep working for years with little maintenance. However, if your air conditioner suddenly fails to start up one day despite your best care, the capacitor might be to blame. Though small, capacitors play a big role in your air conditioner’s daily functioning.

What is a Capacitor?


A capacitor is a small cylindrical device inside your air conditioning unit that supplies and stores electrical energy. When your air conditioner is powered on, the capacitor’s job is to provide a high-voltage jolt (around 400 to 600 volts) to the compressor, fan motor, and blower motor. 

After the capacitor jumpstarts those parts, your AC will begin blowing cold air throughout your home. While your air conditioner is running, the capacitor collects and stores energy, similar to a rechargeable battery. Each time your air conditioner turns on, the capacitor provides a new blast of energy. Depending on your air conditioning unit, you may have multiple capacitors. 

Why Good Capacitors Go Bad

Capacitors fail every day — they do a tough job and, unfortunately, their work takes a toll. There are a few factors that play heavily into the lifespan of your capacitors, though. These include:

Heat exposure

In Phoenix, perhaps one of the most damaging elements for air conditioner capacitors is the heat. Unfortunately, exposing these units to high heat for extended periods of time greatly shortens their lifespan and can cause significant damage to your unit. We recommend keeping the area around your AC clean and shaded, if possible. 

Voltage rating

All capacitors have a voltage rating, which informs air conditioner technicians which capacitor is right for that unit. Unfortunately, homeowners may try to cut costs by choosing to replace their capacitors themselves without understanding how to choose the right one. An undersized capacitor won’t hurt your air conditioner, but it will shorten the capacitor’s life significantly. If you decide to DIY this job, remember that bigger is better — if your air conditioner is a 370- volt unit, bumping up to a 400-volt capacitor will ensure you get enough power and it reaches its maximum life expectancy.


Capacitors have a limited life span. Most are designed to last approximately 20 years, but a number of factors can cause them to wear out quicker. If your air conditioner cycles much more rapidly than average, your capacitor is undersized (as mentioned above) or it’s 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.

If your air conditioner is refusing to start, running with little enthusiasm, making weird noises, or just isn’t cooling right, give Precision Air a call. All of our technicians are NATE certified and trained to handle any sort of problem your air conditioner can throw at them. Remember, we don’t charge weekend fees or add trip charges to your bill, and we’ll come out when it’s convenient for you. A quick call to 480-680-9825 is all it takes to schedule your appointment, 24 hours a day, seven days a week!