The Impact of a Faulty Capacitor on Your HVAC System

hvac capasitor info from alpha mechanicals


Jake Smith, Online Marketing Strategist
Technically Reviewed by Jake Smith, Online Marketing Strategist on Oct 08, 2023 | Written by Alpha Mechanical Editorial Contributors

When you walk into your home on a hot Sacramento valley summer day, without even knowing the proper operations of HVAC systems you will quickly realize your AC is not running properly. Or if you notice your air conditioner producing a humming noise or burning smell from its outside unit or your AC having startup problems or turning off, this may indicate your AC capacitor is bad. Your HVAC performance relies heavily upon this device, capacitor to operate at all let alone effectively. Although there are a lot of moving components to the equipment that keeps your air conditioner, having a failing HVAC capacitor will lead to bigger problems and inconsistent cooling and heating. In this article, we will be going over what a capacitor is, bad HVAC capacitor symptoms, testing the capacitor, as well as maintenance importance.

What is an HVAC Capacitor and How Does a HVAC Capacitor Work?

The heating and air conditioning system in a home has a multitude of critical parts that work together in order to achieve the set temperature. One of these important pieces is the AC capacitor, which helps start up the compressor. A capacitor delivers voltage or the initial energy burst to turn the system on when a new air conditioning or heating cycle begins. This component is shaped similar to a soda can and stores energy in an electrostatic field which stabilizes the power it brings to startup the HVAC unit. The initial voltage burst runs between 300-500% of the normal electrical power needed for the system to operate effectively. There are multiple capacitors for each motor found within the system including the compressor, blower and outdoor fan which means the location of this part will vary depending on the type of air conditioner it is. A set of these capacitors gives the power and the other stabilizes it to keep the system running. Without a good capacitor these motors could run at a higher amplification leading to motor overheating. When there is a capacitor malfunction it could even stop running altogether. The capacitor’s are designed to last between 5-10 years depending on the brand.

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Why Capacitors in HVAC Systems are Important?

Capacitors may seem like an insignificant part of your HVAC System, however, if you have a failing AC capacitor, your unit will not be able to properly turn on as it was designed to. By understanding how capacitors work and the value in replacing them when it is needed, you can ensure that your home in the Sacramento area has a unit that runs smoothly with little reduced efficiency or complications in start up. If your HVAC capacitor is bad, the motor will run at higher amplification, run backwards or stop running altogether. Investing in the health of your HVAC system will save you time and money including your HVAC tune-up in Sacramento.

List of Bad AC Capacitor Symptoms.

If your air conditioning unit is in need of a replacement capacitor, there are some AC capacitor symptoms you’ll probably notice. These include:

Warm Air

When your HVAC capacitor is damaged your air conditioner may be running but begin to blow warm air into your home. If your thermostat is blank and your AC is not working, you may have another issue. If after troubleshooting your thermostat, the issue persists you may need to check the capacitor as the source of the problem. When you have a faulty capacitor, the compressor isn’t able to start properly which means that the air conditioner isn’t able to remove the heat and transfer it outside, instead it blows it into your home. The warm air that is already in your ducts begins to circulate as the blower motor runs which could lead to fan motor issues and compressor damage.

Humming Noises

Another sign of capacitor failure is a humming sound coming from within the access panel. One way to troubleshoot if it is in fact the air conditioning where the noise is coming from is to turn the AC unit off and on once again to determine if that is the case. By doing this step you will hear if the humming racket continues, it is likely that the capacitor has gone out. Call for a professional inspection if the issue persists in order to diagnose a failing HVAC capacitor. Having an HVAC expert assess this component replacement or performing an HVAC tune-up checklist will ease your mind on any further issues arising.

Burning Smell from Condenser Unit

The capacitor is responsible for supplying the force to the AC compressor to start up the unit, so when it fails, the compressor will also fail. When you smell anything burning from within your outdoor AC system, this could indicate that your motor is overheating. Oftentimes the bearings in the system will wear down over time from having to overexert or just normal wear and tear. For a quick fix, the bearings can be lubricated, however, eventually HVAC capacitor replacing is necessary.

Increased Energy Consumption

Another one of the bad HVAC capacitor symptoms to look for is an increased energy bill due to higher energy consumption rates. This could be the result of a system that is overexerting itself to turn on during its cycles or an aging system. Your air conditioner will be straining itself to cool down the air, lowering the unit’s voltage rating and overall effectiveness of this electrical component. When you use HVAC with a bad capacitor it will produce lower voltage which will waste energy and money if left not repaired. An old capacitor is subject to burning out and an older system will continue to malfunction with the only solid solution being to replace the unit entirely. Calling your local Sacramento expert for an HVAC system replacement cost estimate.

Air Conditioner Turns Off Suddenly

One of the most common causes of an air conditioner shutting off suddenly is a bad AC capacitor. Every once and a while the unit may shut off from a tripped circuit breaker, but when it short circuits continuously, the system needs to be evaluated by a professional. The condenser unit dispels the hot air to keep your home cool but if the air conditioning turns off randomly, this is a sign the problem lies in the capacitor. Of all the common bad capacitor symptoms, having a faulty air conditioner turn-off or experiencing power fluctuations is the most alarming.

Air Conditioner Unit Doesn’t Turn On

When your unit takes more than 30-60 seconds to turn on or fails to turn on at all, this is cause to check your capacitors. If your HVAC system turns off on its own or hesitates to start up or fails to start, these checklist issues all point to a capacitor issue. If you are able to, remove the side panel to assess the situation and double-check the voltage in order to give an HVAC technician the information they may need to diagnose capacitor failure until they are able to see your unit in person for HVAC capacitor repairing.

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The Factors Responsible for Bad HVAC Capacitor Symptoms

1. Extremely high temperatures:

If you are located in the Sacramento, California region, extremely high temperatures and thunderstorms aren’t typically something you have to be concerned about. However, if you live in an area where you experience frequent power surges and lightning strikes as a result of living in a hot region, these high temperatures outside can affect our outdoor air conditioning units with a quicker rate of wear and tear. This can overheat the system’s circuitry and cause it to fail.

2. Microfarad Rating:

A “microfarad rating” is a specific charge of electrons which is to be maintained for the system to work properly. This rating must match the requirements of the HVAC system’s motor. If the rating is too low, the motor may run slow or not at all. If the rating is too high, it could cause the motor to overload and fail.

3. Aged Capacitor or AC unit:

On average AC capacitors last between 10-20 years with proper maintenance. However, this will also depend on whether you have the most reliable HVAC brand or not. If your capacitor has never been replaced or had a maintenance inspection, it is important not to cut corners and bite the bullet of replacing to ensure not to cause any worse issues to your system.

How Can a Bad Capacitor Affect Your HVAC Systems?

Capacitors support the motor system within your HVAC unit by turning them on and keeping them running smoothly. The importance of capacitors in HVAC systems is unmatched by any other component so the unit will fail if it is not fixed. Although your unit may continue to run, it is not wise to continue using the air conditioner before replacing a failing capacitor as it can lead to compressor failure and fan motor issues as well as system failure. Other factors inside the air conditioners can sustain damage as a result of a bad capacitor such as overheating the system. HVAC capacitors replacement cost can vary depending on the make and model of your unit as well as the type of capacitor to be replaced.

How to Test Your HVAC Capacitor?

If you are unsure on HVAC facts and the ins and outs of your heating and cooling system, you may not be aware that your air conditioning unit has a capacitor until it fails on you. Fortunately, identifying a bad AC capacitor is relatively straightforward for a technician. A licensed HVAC professional will come with a multimeter to test the voltage rating across the capacitor terminals. Because the capacitor stores energy that it releases to help the motor start, it has to be set to s specific microfarad rating. If the voltage reading is too low, the capacitor is likely defective and needs replacing. If the capacitor is bulging, corroding or cracked in its casing, these are all visual indicators as well. Replacing an AC capacitor is an uncomplicated process and can take less than an hour for a technician to complete. After the bad capacitor is disconnected from the system, the mounting brackets and wires will need to be removed in order to install the new one in its place and join the writing to the new capacitor before they test the new capacitor.

Wrapping Up

Although capacitors are a small piece to the puzzle that makes up your heating and cooling system, they are crucial for an efficient and smooth running operation. Learning the system and being able to narrow down your air conditioning issues is an important part of being a homeowner. No one wants to experience warm air blowing into their home or an AC that won’t turn on at all, it is important to rule out a failed capacitor as a factor by contacting your local Sacramento, CA HVAC technician for guidance and inspection.

Frequently Asked Questions

Can my HVAC run on a bad capacitor?

If your air conditioner is still running despite having a faulty capacitor, using your cooling system while this component is failing will lead to compressor and/or system failure.

Is a capacitor something I can replace by myself?

Capacitors operate like a battery and carry a lot of power and your unit make and model matters when it comes to the appropriate size of the capacitor for the system. It is recommended to hire a professional for the job.

Can a bad capacitor affect the thermostat?

If you set your thermostat to a specific temperature and continue to lower that temperature if you find your system not kicking on or blowing warm air, the unit will begin to overheat faster from overexertion. Your thermostat will read that number correctly if it is working properly, however, your outdoor unit should not affect the health of your thermostat overall.

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