One of the most common reasons for an air conditioner to stop cooling is a bad capacitor.
And while it’s relatively simple to replace and get your system back up and running, you may be curious why it failed in the first place and how long you should expect it to last.
As a licensed HVAC contractor, I have diagnosed and replaced hundreds of capacitors.
I have seen capacitors outlast the air conditioner they were installed in and I’ve seen capacitors fail after 2 years.
AC Capacitor Lifespan of 10-20 Years
The lifespan of an AC capacitor is between 10 and 20 years.
Bad capacitors are a very common issue during the summer months when air conditioners are running at their hardest.
The nature of the capacitor and the job it performs cause a lot of wear and tear and can cause it to fail.
Warranty Length of 1-5 Years
Some manufacturers will warranty their capacitors for up to 5 years, which in my experience is much less than it actually lasts.
Others will only guarantee it for a year, but realistically if the unit is maintained and functioning properly the capacitor should last a good deal longer than the warranty.
Extreme Temperature And Humidity Lowers Life Expectancy
Extreme heat will cause your air conditioner to work overtime.
Your capacitor doesn’t handle this very well and will wear quicker because of it.
The same is true for high humidity and low temperatures. We tend to run our A/C at lower temperatures to reduce humidity even when the temperature isn’t very high.
This can cause your system to short cycle and put additional strain on your capacitor.
High Voltage And Current
High voltage and/or current is another factor that will negatively affect your capacitor.
These parts have limitations and are only rated for certain values. If these values don’t match the ratings, premature failure is inevitable.
5 Reasons Why AC Capacitors Go Bad
Reason 1: Short Cycling
An air conditioner that short cycles, cycles on and off too quickly, is a major reason for capacitors to fail prematurely.
Short cycling is bad for all A/C components, but the strain it puts on your capacitor greatly reduces its lifespan.
The most wear and tear it sees is when the compressor first starts.
The increased load from your system turning on and off more frequently than it should will wear it out and cause it to fail.
Reason 2: Too Much Heat
The capacitor is full of oil and under high heat conditions that oil will expand and cause it to fail.
Most of the time it will bulge or ‘pop’ and can be identified pretty easily.
This is one of the most common capacitor failures seen in air conditioners because of the environment that they’re in.
Typically running in the sun on the hottest days creates the perfect situation for them to fail.
They also can’t hold a charge while overheating and will eventually wear out over time.
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Reason 3: Wrong Voltage Or Rating
Capacitors have voltage ratings and are measured in microfarads.
All motors and compressors are rated for certain size and voltage capacitors.
If the wrong capacitor is installed for the wrong equipment, it will have a decreased life expectancy.
Not only will the part itself fail, it can also damage the compressor or fan motor it’s being used for.
Both oversized and undersized capacitors will damage your equipment so it’s important to use the proper size when replacing.
Reason 4: Old Age
Sometimes capacitors just wear out once they’ve reached a certain age.
Unfortunately parts don’t last forever and eventually repairs are necessary.
If you’re lucky and you maintain your equipment, your capacitor may last the entire life of your air conditioner, but most people have to replace theirs at least once.
Reason 5: Storms and Power Surges
Thunderstorms and power outages cause an increase in failed capacitors.
Any time the power surges, the increased voltage will negatively effect the components in your air conditioner and can damage them to the point that they can no longer function properly.
AC capacitors aren’t designed to handle the heat and surge from these situations and can inevitably fail.
First Signs of Bad Capacitor Is Cool Air
The first sign is that you don’t have cool air blowing in.
You may notice that your lights keep dimming and hear a humming sound coming from your outdoor unit. It may take several tries to start and run properly or it may not turn on at all.
Frequently Asked Questions
How often do A/C capacitors go bad?
Capacitors are a common failed part and usually last around 10-20 years.
Most people will have to replace theirs at least once during the lifespan of their equipment.
Is it okay to run A/C with a bad capacitor?
It is not recommended to continue running your equipment if you have a bad capacitor.
Compressor and fan motor windings will overheat without the proper voltage and current from the capacitor and cause additional repairs to be needed.
What causes an A/C capacitor to keep going out?
Frequently having a bad capacitor may be a sign of short cycling equipment or power related issues.
Increased wear and tear from short cycling or voltage surges and fluctuations will increase the chance that your capacitor will fail.
What happens if you touch an A/C capacitor?
If the capacitor has not been properly discharged, you’ll be shocked if you touch it.
Most are rated at 370-440 volts and create quite the jolt if you happen to be on the receiving end. Always properly discharge a capacitor before handling.
Do A/C capacitors wear out?
Yes, capacitors like all other parts will wear out over time.
The environment its in as well as the job it does cause a high amount of wear and tear and will cause it to fail after so long.
How much does it cost to replace an A/C capacitor?
Most homeowners can expect to pay a contractor on average between $175-$200 to have their capacitor replaced.
Some prices can be as high as $400 depending on the contractor and how expensive the part is. If you replace it yourself, a capacitor is going to run you $10-$30.
What Are The Different Types of Capacitors?
Two types of capacitors are found in AC units; start capacitors and run capacitors.
Start capacitors are used only when your condenser first turns on and gives the compressor an extra boost to start smoothly and efficiently.
Once started, a relay opens and stops the start capacitor from providing too much voltage to the windings. If left on, the windings will overheat and damage the compressor.
The run capacitor is used all the time and provides the proper voltage and current necessary for the motors to run.
Most A/C capacitors are dual capacitors and work for both the compressor and the condenser fan motor.