How to Test an AC Capacitor: Easy Step-by-Step Guide
Air conditioner capacitors store electrical energy, and when they malfunction, it can cause your AC unit to run inefficiently or not at all.
Testing an air conditioner capacitor is relatively simple.
Nevertheless, it will require you to know a few things about your AC unit first.
By understanding how an air conditioner capacitor works and what tools are needed to test one, you can quickly identify any issues before they become unfixable.
This guide will provide step-by-step instructions on how to test both start capacitors and run capacitors.
We’ll also discuss different types of AC capacitors and their function in the overall operation of an air conditioning system.
Keep reading to learn how to diagnose a capacitor problem in your AC.
What is an AC Capacitor and How Does It Work?
An air conditioner capacitor is an essential component of a home air conditioning unit.
It is typically found near the fan blades or coils of the AC unit.
Its primary function is to store and supply power for your system’s motors.
In simple terms, it acts as a surge protector, providing a jolt of electricity to get your AC up and running when you first turn it on.
The amount of electricity required to turn on an AC can be quite high.
As such, the capacitor helps reduce this load by storing energy in powerful bursts.
This helps increase the speed at which your air conditioner starts up.
It can also help with reducing wear and tear on its components.
After the initial start-up phase, the capacitor reduces its output to a steady current that powers your system until it shuts off.
Air conditioner capacitors come in different sizes and are measured in voltage and microfarads (MFD).
Voltage measures how fast electrical current moves through the capacitor.
Meanwhile, MFD indicates how much electrical current it can store.
Most capacitors range from 5 MFD to 80 MFD, depending on their size and model.
A larger capacitor will typically have more voltage and MFD than smaller models.
This means they can handle higher loads of electricity without overloading the system or causing damage.
While all capacitors serve similar functions, they should not be used interchangeably.
Since they are designed for certain types of air conditioning systems, using them on an incompatible system can lead to irreversible problems.
If you’re unsure about what type of capacitor is right for you, contact your local HVAC specialist.
They can help you identify what type of capacitor works best for your AC unit.
What Is a Dual-Run Capacitor?
A dual-run capacitor is a combination of two capacitors in one unit.
It powers the fan motor and compressor motor simultaneously, helping reduce the amount of energy needed to start up your AC unit.
Dual-run capacitors are more common than single-run models as they help improve efficiency while also reducing wear and tear on the components.
Start and Run Capacitors: What Are They?
Modern AC units have two types of AC capacitors: a start capacitor and a run capacitor.
Let’s look at each type before moving on to our step-by-step guide:
A start capacitor is a temporary capacitor that helps get the motor running.
This type of capacitor has a higher voltage rating and will only be used for a few seconds when you first turn on your AC.
The run capacitor, on the other hand, works to maintain continuous power flow to the motor after the initial start-up phase.
It has a lower voltage rating and stays charged until the AC is turned off.
Its main function is to ensure that the fan or compressor motor runs efficiently without straining or overheating.
Step-by-Step Instructions on How to Test AC Capacitor
Now that we’ve gone over what an AC capacitor is and the two types of capacitors used in modern ACs, let’s take a look at how to test the capacitor.
Materials & Tools Needed to Test an AC Capacitor
To test an AC capacitor, you’ll need the following materials and tools:
- Insulated gloves
- Voltage tester
Step 1: Wear Insulated Gloves
Before beginning, make sure to wear insulated gloves for safety.
Additionally, double-check that your AC has been turned off, to avoid harmful and unwanted accidents.
Step 2: Locate the Capacitor
As mentioned earlier, the capacitor is typically found near the AC fan motor or compressor.
Use your screwdriver to open your AC unit and find the AC capacitors.
You’ll see some wires connecting your AC components to the start and run capacitor.
Take a picture of the wires to use as a reference when you reconnect them later.
Step 3: Discharge the Capacitor Terminals
Capacitors that are in good condition can carry charges for hours up to months after being unplugged from their main power source.
Before anything else, make sure to discharge the capacitor terminals to avoid harmful accidents.
Using the metal shaft of your screwdriver, short the terminals connecting your AC unit to the capacitors.
Keep your fingers as far away from the screwdriver’s metal shaft as possible.
It may take a few minutes for the energy to evacuate the air conditioner capacitor.
Step 4: Check voltage rating and Remove Wires
Check the voltage on the capacitors using a voltage meter or multimeter.
Using a pair of pliers, remove the wires connected to your air conditioner capacitor.
Now, you can test your capacitor’s “capacitance” levels.
Step 5: Set Multimeter
You can use two types of multimeters to test a capacitor: an analog or digital multimeter.
A digital multimeter is easier to use than an analog meter. However, we’ll walk you through how to use each type.
How to Use a Digital meter
Set your digital meter to “capacitance.”
Using the probes provided with the multimeter, touch one end of each capacitor terminal.
If the readings are below the stated capacitance setting on your AC manual, you likely need a new capacitor.
How to Use an Analog meter
If you’re using an analog meter, connect the probes to each capacitor terminal.
Turn your dial until you reach the capacitance setting and observe the needle’s deflection.
Again, if the needle does not move far enough or points below the stated capacitance value on your AC capacitor, it likely needs replacement.
Tips for Troubleshooting AC Capacitor Issues
If you experience any issues while testing your AC capacitor, here are some tips to help troubleshoot them:
- Make sure all connections are secure and firmly in place.
- Inspect the capacitor for any signs of corrosion or damage to the casing.
- Check that all wiring is intact and properly insulated.
- Use a quality multimeter to ensure you’re getting an accurate reading.
When all else fails, it is best to seek professional help from an HVAC technician.
Signs of a Bad AC Capacitor
A bad AC capacitor can be tricky to spot. Fortunately, there are signs that can help you identify an AC capacitor problem.
Compressor or Condenser Fan Motor Won’t Start
The first sign you’ll notice when dealing with a bad AC capacitor is a dysfunctional compressor or fan motor.
Since your AC capacitor is not supplying enough energy for either component, it makes it harder for them to maintain functionality, if they manage to turn on at all.
Another sign that your AC capacitor has gone bad is if your AC stops producing enough cold air for your home.
This is because your unit might not be receiving sufficient energy to keep things running.
Higher Energy Bills
The condenser fan motor has to work harder to make up for a faulty AC capacitor.
You can expect lesser efficiency and higher energy bills as a result.
Since your fan motor needs to work twice as hard to keep up with the demands of your home, a faulty capacitor can also shorten the life expectancy of your unit.
In other words, you may have to replace your AC unit sooner than you thought.
When to Seek Professional Help
If the AC capacitor in your system has gone bad, it is best to replace it as quickly as possible.
Testing an AC capacitor is not a difficult task as long as you know what you’re doing.
If you arm yourself with the right materials and tools, as well as understand how to use them properly, you can easily test your AC capacitor for any faults.
If all else fails, seek professional help from an HVAC technician who can handle the job safely and efficiently.
A specialist can also detect any other underlying issues in your AC unit that could be causing a problem and make the necessary repairs.
Reliable and Effective Solutions to All Your HVAC Needs
Having a malfunctioning air conditioner can be incredibly frustrating and inconvenient.
Not only is it uncomfortable, but you also run the risk of higher energy bills due to inefficient cooling.
Plus, if your AC capacitor has gone bad, it could shorten the life expectancy of your unit and require costly repairs or replacements.
A qualified and experienced professional can inspect your AC unit, identify any underlying issues, and provide reliable and effective solutions to all your HVAC needs.
One-Stop Heating and Air Conditioning is a trusted provider of HVAC services for homeowners across Sandy, UT.
With years of experience in providing air conditioning and heating systems, we are devoted to making sure that your home is comfortable and energy efficient all year round.
Our team of qualified professionals can provide comprehensive diagnostics of your AC system. We also offer reliable and effective solutions to all your HVAC needs.
Whether it’s a new AC capacitor, AC repairs, or AC maintenance—we can help you get the best results at an affordable price.
Contact (801) 355-9500 for more details.