Step-by-Step: How To Change Air Conditioner Capacitor Yourself

Can you change an air conditioner capacitor yourself? Yes, you often can. It is a common AC unit DIY repair for many homeowners. What is an AC capacitor? It is a small, cylinder-shaped part. This part gives your AC motor a quick jolt of power. It helps start both the compressor and the fan motor in your outdoor unit. If your AC is not cooling, or you hear an air conditioner humming noise, a bad capacitor is often the problem. This guide will show you how to do it safely.

Grasping the AC Capacitor’s Purpose

An AC capacitor is vital for your air conditioner. It stores an electrical charge. Think of it like a small battery. When your AC unit turns on, the capacitor releases this charge. This burst of power helps start the AC fan and the compressor. Without this jolt, these parts cannot begin to spin or pump. They will just hum or sit still. A bad capacitor means your AC unit will not work right.

The capacitor helps your AC unit start easily. It uses less power to get going. This part helps your AC run smoothly too. It keeps the electrical flow steady. This makes your AC unit last longer. It also helps it cool your home well.

Signs of a Failing AC Capacitor

How do you know if your AC capacitor is bad? There are clear signs. Pay attention to these warnings. They can save you from bigger AC problems later. Spotting them early helps with AC not cooling troubleshooting.

The AC Unit Won’t Start

This is a common sign. You turn on your AC. You hear nothing. Or you hear a click, but nothing else happens. The outdoor fan does not spin. The compressor does not turn on. This often means the capacitor is too weak. It cannot give the motor enough power to start. This is a key sign of a compressor not starting AC issue.

The Outdoor Fan Does Not Spin

Sometimes, the AC fan not spinning repair is simple. The outdoor fan blade might try to spin. But it moves slowly. Or it just shakes a little. You might even be able to push it with a stick to get it started. Do not do this too much. If the fan needs a push to start, the capacitor is likely weak. It is not sending enough power to the fan motor.

Air Conditioner Humming Noise

You might hear a loud humming sound. This noise comes from the outdoor unit. It means the compressor or fan motor is trying to start. But it cannot. The capacitor is not giving enough power. The motor is straining. This air conditioner humming noise fix often means changing the capacitor. A constant hum with no cool air points to a bad capacitor.

Warm Air from Vents

Your AC unit runs. The fan is blowing inside your home. But the air is not cold. It feels warm or just like a fan blowing room air. This is a common AC not cooling troubleshooting problem. If the outdoor unit’s compressor is not running, it cannot cool the refrigerant. The capacitor helps start the compressor. So, if the compressor is not starting, the capacitor could be the reason.

Higher Electric Bills

A failing capacitor makes your AC work harder. It tries to start motors without enough power. This uses more electricity. You might notice your power bill going up. This happens even if you use your AC the same amount. An old capacitor makes your AC less efficient. It costs you more money.

Visible Bulging or Leaking

This is a visual check. Always turn off power first. Look at the top of your capacitor. Does it look swollen or bulging? Does it seem to have liquid leaking from it? These are sure signs of a failed capacitor. A good capacitor looks flat and clean on top. Any bulge means it has failed.

Safety First! Discharging the AC Capacitor Safely

Safety is the most important step. Electricity can harm you. Capacitors store a lot of power. They can hold a charge even after power is off. You must discharge AC capacitor safely before you touch it. Do not skip this step.

Turning Off Power

1. Find the Disconnect Box: This box is outside, near your AC unit. It has a pull-out handle or a switch.
2. Turn Off at Breaker: Go to your home’s main electrical panel. Find the breaker for your outdoor AC unit. It might be labeled “AC,” “Furnace,” or “Condenser.” Turn it OFF. This is the safest way to cut all power.
3. Confirm Power is Off: Use a non-contact voltage tester. Touch it to the wires inside the AC unit. Make sure there is no power. The tester will beep or light up if power is still on. Do not touch anything until the tester shows no power.

Discharging the Capacitor

This step removes any stored electricity.

1. Gather Your Tools: You need an insulated screwdriver or a pair of pliers with insulated handles. Make sure the handles are rubber-coated.
2. Locate the Terminals: The capacitor has terminals on top. These are metal prongs where wires connect. There can be two, three, or four terminals.
3. Short the Terminals: Hold the insulated screwdriver by its handle. Touch the metal shaft of the screwdriver across two terminals at the same time. You might hear a small pop or see a spark. This is normal. It means the capacitor has discharged.
4. Repeat for All Terminals: If your capacitor has three terminals (Herm, Fan, C), you need to discharge all pairs.
   • Touch “Herm” and “C.”
   • Touch “Fan” and “C.”
   • It is a good habit to touch all pairs to be sure.
5. Re-check: After discharging, touch the screwdriver across the terminals again. Make sure there are no more sparks. This confirms it is safe to handle.

Tools for AC Capacitor Change

Before you start, gather your tools. Having the right tools for AC capacitor change makes the job easier and safer.

• Insulated Screwdriver: A good quality one is key for discharging the capacitor. Make sure it has a rubber or plastic handle.
• Nut Driver Set or Wrench: To remove the access panel screws. Sizes vary, often 1/4 inch or 5/16 inch.
• Needle-Nose Pliers: Useful for gently pulling off wire terminals.
• Work Gloves: Protect your hands.
• Safety Glasses: Protect your eyes from sparks or dust.
• New Capacitor: Make sure it is the correct type and rating. More on this later.
• Digital Multimeter (DMM) with Capacitance Setting: This is crucial for HVAC capacitor test. It helps you check if the old capacitor is truly bad and if the new one is good.
• Digital Camera or Smartphone: Take pictures of the wiring before you disconnect anything. This is a must for the run capacitor wiring diagram.

How to Test Your AC Capacitor

Testing your AC capacitor confirms if it is bad. This step saves you time and money. Do not just replace it based on symptoms. Always test it first. You will need a digital multimeter with a capacitance (µF) setting. This is your HVAC capacitor test kit.

Steps to Test the Capacitor

1. Turn Off All Power: Follow the safety steps above. Turn off the breaker and disconnect switch.
2. Discharge the Capacitor: Use your insulated screwdriver. Touch the terminals to safely discharge any stored power. This is very important.
3. Disconnect Wires: Carefully remove the wires from the capacitor terminals. Use needle-nose pliers if needed. Take a photo of the run capacitor wiring diagram before you remove wires. This is your guide for putting them back.
4. Set Your Multimeter: Turn your multimeter dial to the capacitance setting (µF or nF symbol). Some meters auto-range.
5. Connect Probes: Touch the red probe to one terminal and the black probe to another terminal.
   • For a two-terminal capacitor: Touch one probe to each terminal.
   • For a three-terminal capacitor (common for dual run capacitor replacement):
     • Test “C” (common) to “Herm” (compressor).
     • Test “C” (common) to “Fan” (fan motor).
     • The values you get should match the microfarad (µF) ratings on the capacitor label. For example, a 40/5 µF capacitor should read around 40 µF from C to Herm, and 5 µF from C to Fan.
6. Read the Display: The multimeter will show a reading in microfarads (µF). Compare this number to the rating printed on your capacitor.
   • Tolerance: Capacitors usually have a tolerance. This is often +/- 5% or 10%. So, a 40 µF capacitor is good if it reads between 38 µF and 42 µF (for +/- 5%).
   • Zero or Very Low Reading: If your multimeter reads zero or a very low number (like 0.1 µF for a 40 µF capacitor), the capacitor is bad.
   • High Reading: A reading much higher than the rating also means it is bad.

If your old capacitor fails this test, it is time for a replacement.

Choosing the Right Replacement Capacitor

Choosing the correct replacement capacitor is crucial. Using the wrong one can damage your AC unit. Always match the new capacitor to the old one’s specifications.

Key Specifications to Match:

1. Microfarad (µF) Rating: This is the most important number. It tells you the capacitor’s storage capacity.
   • Single Capacitors: Have one µF rating (e.g., 35 µF).
   • Dual Run Capacitors: Have two µF ratings (e.g., 40/5 µF). The first number (40 µF) is for the compressor. The second number (5 µF) is for the fan. These are used in dual run capacitor replacement. The terminals will be labeled “C” (Common), “Herm” (Hermetic for compressor), and “Fan.”
2. Voltage (VAC) Rating: This tells you the maximum voltage the capacitor can handle. Your new capacitor’s voltage rating must be equal to or higher than the old one. Never use a capacitor with a lower voltage rating. Most AC capacitors are rated for 370 VAC or 440 VAC. A 440 VAC capacitor can replace a 370 VAC one, but not the other way around.
3. Physical Size: While not critical for electrical function, the new capacitor must fit in the space of the old one. Check the height and diameter. If it is slightly taller, it might still fit.
4. Terminal Type: Most AC capacitors use spade terminals. Make sure the new one has the same type.

Where to Find the Information

All these details are printed on the label of your old capacitor. Take a clear photo of the label before you buy a new one. This ensures you get an exact match. You can buy replacement capacitors at HVAC supply stores or online. Make sure you buy from a trusted seller.

The Step-by-Step Replacement Guide

Now, let’s replace that old capacitor. Take your time and follow each step carefully. Remember your photos for the run capacitor wiring diagram.

h4. Step 1: Prepare the Area

1. Turn Off Power (Again!): Go back to your main electrical panel. Turn off the breaker for your outdoor AC unit. Then, remove the disconnect switch handle near the unit. Use your non-contact voltage tester to confirm no power is present. Safety first, always.
2. Remove the Access Panel: Use your nut driver or wrench. Unscrew the bolts holding the access panel to your outdoor unit. This panel covers the electrical components, including the capacitor. Gently remove the panel. Set it aside where it won’t get damaged.

h4. Step 2: Locate and Photograph the Capacitor

1. Find the Capacitor: It is a large, cylinder-shaped object. It often stands upright. It might be black, silver, or another color.
2. Take Pictures: Use your phone or camera. Take several clear pictures of the capacitor and its wiring. Get close-up shots of how each wire connects to the terminals. This is your essential run capacitor wiring diagram. It will help you put the new one back correctly. Mark the wires if you need to, but photos are best.

h4. Step 3: Discharge the Old Capacitor Safely

1. Get Your Insulated Screwdriver: Hold it by the insulated handle.
2. Discharge Terminals: Touch the metal shaft of the screwdriver across the terminals of the capacitor.
   • For a two-terminal capacitor, touch both terminals at once.
   • For a three-terminal capacitor (common for dual run capacitor replacement), touch “C” to “Herm” and “C” to “Fan.” You might see a small spark or hear a pop. This is normal and means it is discharging.
3. Confirm Discharge: Repeat the touching process a few times. Make sure no more sparks or pops occur. This confirms it is safe to touch.

h4. Step 4: Disconnect and Remove the Old Capacitor

1. Disconnect Wires: Carefully remove the wires one by one from the capacitor terminals. Use needle-nose pliers if the terminals are tight. Pull on the connector, not on the wire itself.
   • As you remove each wire, check your photos. Make sure you know which wire goes to which terminal (C, Herm, Fan).
   • You can label the wires with tape if it helps.
2. Remove Mounting Bracket: The capacitor is usually held in place by a metal strap or clamp at the bottom. Unscrew the bolt holding this strap.
3. Lift Out the Old Capacitor: Gently lift the old capacitor out of the unit.

h4. Step 5: Install the New Capacitor

1. Place the New Capacitor: Put the new capacitor into the mounting bracket. Make sure it sits securely.
2. Secure the Bracket: Tighten the bolt on the mounting strap. The capacitor should be firmly held in place. It should not wobble.
3. Connect Wires (Use Your Photos!): This is where your wiring diagrams come in handy.
   • Match the wires to the correct terminals on the new capacitor.
   • Common (C) Terminal: This terminal usually has several wires connected to it, often brown or white wires.
   • Herm (Hermetic/Compressor) Terminal: This terminal usually has a brown wire.
   • Fan (Fan Motor) Terminal: This terminal usually has a purple or yellow wire.
   • Push each wire connector firmly onto its correct terminal. Make sure they are snug. Wiggle each connector to confirm it is tight.
   • Refer to your photos often. Do not guess.

Note: Wire colors can vary by manufacturer. Always rely on the terminal labels (C, Herm, Fan) and your photos.

h4. Step 6: Test the New Capacitor (Optional, but Recommended)

Even if it’s new, it is a good idea to quickly test the new capacitor before sealing everything up. This confirms it is not a dud.

1. Discharge the New Capacitor: Yes, even new ones can have a small charge. Always discharge it first using your insulated screwdriver.
2. Test with Multimeter: Set your multimeter to the capacitance setting. Touch the probes to the correct terminals as you did for the old one (e.g., C to Herm, C to Fan).
3. Check Reading: The reading should be very close to the µF rating on the new capacitor’s label, within its tolerance. If it is good, proceed. If it shows zero or a bad reading, you have a faulty new capacitor. Get a replacement.

h4. Step 7: Final Steps and Power On

1. Replace the Access Panel: Put the access panel back onto your outdoor unit. Screw it securely into place.
2. Restore Power: Go back to your main electrical panel. Turn the AC breaker back ON. Go to the outdoor unit. Replace the disconnect switch handle.
3. Test Your AC Unit: Go inside your home. Set your thermostat to cool. Lower the temperature setting below your room temperature.
4. Listen and Observe:
   • Does the outdoor unit turn on?
   • Does the fan spin quickly and smoothly?
   • Do you hear the compressor running (a steady hum, not a struggling one)?
   • Is cold air coming from your vents?
   • If yes, you have fixed your AC unit DIY repair!

Common Issues After Replacement

Sometimes, things do not go perfectly. Here are a few common issues you might face after changing your capacitor and how to fix them.

• AC Still Not Working:
  • Check Power: Make sure the breaker is on. Make sure the disconnect switch is fully inserted.
  • Check Wiring: Did you connect all wires correctly? Refer to your photos again. A common mistake is mixing up Herm and Fan wires on a dual capacitor.
  • Check Capacitor Test: Did you test the new capacitor? It might be faulty.
  • Other Problem: The capacitor might not have been the only problem. You might have another issue like a bad fan motor or compressor.
• Fan Spins, But No Cold Air: This often means the compressor is not running. Check the wire connection to the “Herm” terminal on your dual run capacitor. Ensure it is secure. The compressor needs that power.
• Unit Still Humming: If you hear the air conditioner humming noise again, it might mean the capacitor is still not providing enough power, or there is a bigger motor issue. Re-test the new capacitor. If it is good, the motor itself might be bad.
• Burning Smell: Immediately turn off power at the breaker if you smell burning. This means there is a serious electrical problem. Do not try to fix this yourself. Call an HVAC pro.

When to Call a Pro

While changing an AC capacitor is a great AC unit DIY repair for many, sometimes it is best to call a professional HVAC technician.

• You Are Not Comfortable: If you feel unsure at any step, stop. It is okay to call for help. Electrical work can be dangerous.
• Problem Persists: If you replaced the capacitor and the AC unit still does not work, the problem is likely something else. It could be a faulty motor, a bad contactor, or a refrigerant issue. These need expert diagnosis.
• Complex Wiring: If your AC unit has very complex wiring or multiple capacitors, it is safer to let a pro handle it.
• Warranty Concerns: If your AC unit is still under warranty, doing DIY repairs might void it. Check your warranty terms before starting any work.
• Other Issues: If you suspect other major components are bad (compressor, fan motor), a pro can confirm. Replacing these parts is much more complex and costly.

Frequently Asked Questions (FAQ)

Q1: How long do AC capacitors last?

AC capacitors usually last about 5 to 10 years. Their lifespan depends on how often your AC runs. It also depends on the climate and the quality of the capacitor. Hot climates can make them fail faster.

Q2: Can I use a capacitor with a higher µF rating?

No, do not use a capacitor with a higher µF rating. You must match the microfarad (µF) rating exactly. A higher µF rating can harm your AC motor. It can make the motor overheat or fail early.

Q3: Can I use a capacitor with a higher VAC rating?

Yes, you can use a capacitor with a higher VAC (voltage) rating. For example, a 440 VAC capacitor can replace a 370 VAC one. It means it can handle more voltage. It will work fine and is often more durable. But never use a lower VAC rated capacitor.

Q4: What is a dual run capacitor?

A dual run capacitor is a single component. It contains two capacitors inside. It powers both the compressor and the fan motor in your outdoor AC unit. It has three terminals: Common (C), Hermetic (Herm, for compressor), and Fan. This is common for dual run capacitor replacement.

Q5: Is it normal for the capacitor to make a clicking sound?

A clicking sound is usually from the contactor, not the capacitor. The contactor is an electrical switch that sends power to the AC unit’s main components. If the capacitor is bad, the contactor might click but the unit won’t start.

Q6: How often should I check my AC capacitor?

It is a good idea to have your AC unit checked once a year by a professional. They can test your capacitor during this check-up. This can help catch a weak capacitor before it fails completely.

Q7: Can a bad capacitor damage other parts of my AC unit?

Yes, a bad capacitor can damage other parts. If the capacitor is weak, motors might try to start but fail. This causes them to draw too much current. This extra strain can overheat and burn out the fan motor or even the expensive compressor. An air conditioner humming noise fix is important to do quickly.

Q8: Where can I buy a replacement AC capacitor?

You can buy replacement AC capacitors at HVAC supply stores, electrical supply stores, or online retailers. Make sure to buy from a trusted source. Ensure the capacitor meets the exact specifications of your old one. Bring your old capacitor or a picture of its label to the store.

Changing your AC capacitor yourself is a helpful skill. It can save you money and keep your home cool. Always prioritize safety. Follow these steps carefully. If you are ever unsure, call a professional.

Carlos Gadd

My name is Carlos Gadd, and I am the creator of AirPurityGuide.com.. With a passion for footwear, I share my experiences, insights, and expertise about shoes. Through my blog, I aim to guide readers in making informed decisions, finding the perfect pair, and enhancing their footwear knowledge. Join me on this journey to explore everything about shoes!