After spending time in the summer sun, the most refreshing experience is to open your front door and feel a wave of cool air welcome you home. One of the primary parts of your HVAC system that makes the crisp air possible is the air conditioner capacitor.
The AC capacitor is the spark that powers the air conditioner motors. It offers a surge of electricity to initiate operation and then maintains a lower level of energy to keep the HVAC system working properly until your desired indoor temperature is reached.
While the capacitor is a primary component of your cooling system, it’s also one of the most frequently replaced parts. We’ll introduce you to the warning signs that an air conditioner capacitor replacement may be just around the corner, what you can expect to pay for the repair, and why this repair shouldn’t make your DIY list.
What is an AC Capacitor?
The AC capacitor resembles a tall, cylinder-shaped battery. It’s housed in the outdoor unit of your HVAC system or heat pump. Although the capacitor is just a fraction of the size of the unit it powers, when it stops working, the entire system can shut down.
When an HVAC capacitor fails or misfires, your unit may stop blowing cool air or refuse to start at all. The capacitor may look like a battery, but it does far more than simply turn your unit off and on.
When your thermostat detects it’s time for a cool down, it sends the message to your HVAC system. The capacitor plays the lead role, creating an initial burst of electricity that’s up to 500% more powerful than the energy required to simply keep the system running. That jolt of electricity causes the cooling cycle to begin, then the capacitor maintains a steady current of energy to power the unit until your desired temperature is reached.
The capacitor is connected to your air conditioning system via multiple wires. Which means if the part goes bad, it’s much more complicated than opening the unit and popping a new one in. Replacing a central air capacitor is not a DIY job. These high-voltage devices can cause serious injury, even when the power is shut off.
Differences between start and run capacitors
It’s possible for your HVAC system to operate with one capacitor, also called a dual capacitor, or two single capacitors. Both set-ups create the same result: a cooler home.
In a two-capacitor system, a start capacitor and run capacitor are both needed for the system to function properly. The start capacitor is responsible for dispensing the electrical push needed to start the HVAC motor rotation. Once the cooling cycle begins, the run capacitor takes over.
Run capacitors are more common and are responsible for keeping the motor running until your home is comfortably cooled. Think of these two parts like riding a bicycle.
It takes much more effort to get the wheels moving (start capacitor), but once you reach a steady speed, you don’t have to exert so much energy to maintain the motion (run capacitor).
If your system currently operates on two single capacitors and one of the devices fails, the technician may opt to replace both parts with a dual capacitor.
A dual capacitor performs both jobs – initial electrical jolt and steady running power – from a single component. Many technicians prefer using a dual capacitor because it saves space inside the HVAC unit and is simpler to replace when the time comes.
Signs of a bad AC Capacitor
When an AC capacitor replacement is necessary, you’ll experience any number of common symptoms, including:
- Your air conditioner is delayed in beginning a cooling cycle
- Your air conditioner randomly shuts off on its own
- Your air conditioner doesn’t turn on at all
- Your air conditioner sounds like it’s running but doesn’t dispense cool air
- Your air conditioner makes a buzzing or humming noise
- You notice a burning smell or smoke coming from your unit
- Your energy bills are inexplicably high
The capacitor for an AC unit can fail because of age and normal wear and tear, an overheated system, an unidentified short circuit, lightning strikes or power surges, or extremely hot temperatures.
Effects of a bad AC Capacitor
The first sign that your capacitor is no longer working properly is the rising temperature inside your home. The other effects you may not recognize as quickly, but they can be detrimental to your cooling system.
A bad capacitor stops the outdoor unit from doing its job, which means the cooling process can’t be performed. The improper voltage can easily cause damage to other parts of the unit.
Secondly, other components will begin to overwork in attempts to make up for the failed capacitor. The spike in energy demands can create an unexpected increase in your monthly energy bill.
How to test an AC Capacitor
As we mentioned before, the capacitor inside your heating and cooling system can be extremely dangerous when mishandled. For this reason, it’s best to contact a local HVAC repair professional to test or replace your capacitor.
When the technician arrives, they’ll use a multimeter to calculate the capacitor’s current, resistance, and voltage. In simpler terms, they’ll measure whether the capacitor is holding the charge needed to begin and complete the cooling system. If the readings are weak or don’t register at all, then it’s time for an AC capacitor replacement.
Even if you own a multimeter, testing a capacitor isn’t recommended. While dozens of YouTube videos may make the task look effortless, you’re best to skip the DIY approach and call a professional. Capacitor testing can only occur once the power has been shut off, wiring has been disengaged, and voltage remaining in the capacitor has been drained.
It’s a dangerous task, and not one that’s safe to tackle even after watching the most in-depth, how-to video. Rely on a professional.
How long do AC Capacitors last?
HVAC capacitor brands and models can vary slightly in how long they last. On average, an AC capacitor has a lifespan of 10 years. To ensure you get the max from your unit, schedule routine seasonal maintenance on your heating and cooling system.
Annual upkeep on your HVAC system will allow a technician to recognize if there’s a potential problem with the capacitor. Solving the problem before the part completely gives out will save you the headache of locating an emergency HVAC contractor and avoid uncomfortable indoor temperatures in the middle of summer.
AC Capacitor Replacement Cost
The AC capacitor cost of replacement generally falls between $120 and $250, with the majority of repairs landing in the $170 range, as estimated by Home Advisor.
Factors that will play a role in the repair cost include the HVAC capacitor brand, model, and voltage. The actual component generally costs between $9 and $45, but top-rated brand-name parts may be more expensive.
The largest portion of your spend will be labor and installation. The average cost for professional capacitor replacement is between $60 and $200. (For comparison, the typical emergency room visit costs $774, reiterating our advice to hire a professional.) The job should take about an hour for a technician to complete.
Your HVAC system can’t operate properly without an AC capacitor. This small but mighty part is behind keeping your home cool when summer temperatures begin to rise. Schedule your seasonal HVAC maintenance with a professional technician to ensure you get optimal performance from your capacitor and unit as a whole.
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