Has Your HVAC Furnace Capacitor Gone Bad?

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Winter is near; you’ll be relying on your gas furnace, which will offer a lovely ambiance. For the efficiency of your furnace, the capacitor is a modest and crucial component. Its function is an extra jolt of energy to the furnace blower motor, causing the fan to turn on. Like any other part of your furnace, a capacitor can fail and cause your furnace to cease working.

What does the furnace capacitor do?

Because your furnace consumes a lot of energy, it has a capacitor to provide the extra energy required to operate the blower. The capacitor, like a battery, stores the extra energy needed to jumpstart the furnace blower. Capacitors:

  • Store and release energy as needed.
  • They are capable of tolerating higher current loads and have more charge storage capacity.
  • Give an extra burst of energy required to turn the blower motor and get your furnace’s fan spinning.
  • It also stores energy until it is needed.

Do you need to replace a furnace capacitor immediately?

As capacitors are one of the most prevalent components on furnaces, we must give attention to any necessary replacement. But it may typically last between 10-20 years, but the variables could shorten their lifespan. If you’ve had your furnace for more than ten years, you’ll almost certainly need to replace the capacitor at some point.

What are some symptoms of a bad capacitor?

As hot air blows into your home by your furnace’s blower. If a furnace capacitor fails, the blower motor will not perform properly, putting your family’s comfort at risk. There are a variety of signs and symptoms that indicate a defective capacitor:

Power Shutdown

A faulty furnace capacitor will prohibit the blower motor from operating, leading the unit to shut down completely. Check the fuse that controls your furnace to see if it’s on before determining whether the capacitor is the source of the problem.

Increase the thermostat settings once your furnace is powered up and observe whether the blower motor starts working within a few minutes. The capacitor is most likely to be responsible if there is no response.

Inconsistency In Blower Motor

For the blower motor to work effectively, the capacitor must be in good condition. The blower motor may run slowly or inconsistently if the capacitor is defective or overheat readily. If you observe that your blower motor is acting abnormally or has short cycles, have your capacitor inspected by professionals.

Sounds of Humming

The blower’s humming sounds indicate that the capacitor is having electrical troubles. You have no choice but to pay great attention to your blower if you want to solve the problem. To do so:

  • Raise your thermostat and wait for the blower on your heating system to switch on.
  • Open your furnace’s access panel with a screwdriver, then lean near to your blower’s housing to hear the weird noise within.
  • Schedule a professional inspection right away if you hear a buzzing sound.

Stop Blower

A faulty capacitor stops the blower. Check your capacitor soon if your unit stops operating. Make sure the fuse that controls the heating system is turned on before proceeding.

Turn increase your thermostat once the furnace is powered up and see if your blower starts to work within a few minutes. If you don’t get any response from it, your capacitor has likely failed. Call professional for thorough evaluation and diagnosis of your capacitor.

Erratic Motor Operation

Because your capacitor functions as a battery and stores the charge required for the blower motor to operate effectively, it should always be in good working order. On the other hand, your blower motor may run slowly, become excessively hot, and behave abnormally if you have a faulty capacitor. Now, if you notice that your heating system’s motor is constantly short-cycling or acting strangely, contact a professional to have the capacitor tested.

What causes furnace capacitor failure?

Every air conditioning system consists of an electric blower motor that circulates cool air within, an electric condenser fan motor that exhausts hot air outdoors, and a compressor motor that pumps refrigerant through the system.


Each motor has a capacitor to start when the thermostat turns on the air conditioner and keeps it running at maximum efficiency. Because the compressor consumes far more energy than the other two motors, the compressor capacitor is the largest.


The moist separator inside the electrolytic A/C capacitor will dry up if the unit gets too hot, resulting in an internal short circuit. If the capacitor’s temperature consistently exceeds 150 degrees Fahrenheit.


The air conditioning capacitor gets the compressor and fan motors up to about 3/4 of their maximum speed before disengaging them, not for constant electrical load. The capacitor will most likely overcharge and be damaged if the motor becomes physically blocked from turning or if the engine burns out. Voltage exceeding the capacitor’s rated value may also cause it to fail.

Worn-out Part

A capacitor may burn up if the compressor or fan motor drags due to damage or worn bearings. By leaving the capacitor in the circuit for too long, a faulty relay switch might cause it to overheat. A capacitor, a compressor, the fan motor, or the unit’s cables can all be damaged by lightning. Even a minor power surge might cause the capacitor to be damaged or destroyed, resulting in compressor overload and failure. A capacitor that is leaking oil is a dead giveaway that it is malfunctioning.

Life Expectancy

Normal wear will eventually cause an A/C capacitor that has been protected from damage, electrical surges, overheating or inappropriate electrical loads to fail. The lifespan of a capacitor varies depending on the temperature and usage pattern.

Whether you need capacitor assessment, maintenance, or installation, you can trust that we’ll do everything we can to keep you comfortable and safe. Our technicians are ready with methods and techniques to keep your cooling and heating systems in top shape all year. Don’t hesitate to get in touch with us right away. Fill out the contact form below an we will answer any questions you have about your HVAC system.

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