How to Replace an Air Conditioner Run Capacitor

How to Replace an Air Conditioner Run Capacitor

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Once summer hits certain parts of the country, an air conditioning unit is just as important to have as a furnace is in the winter. And just like a furnace, your air conditioner can stop working as efficiently as it should- all which point to a developing problem that will need immediate attention.

Fortunately, many AC issues are easy to troubleshoot, and can help you determine whether a home repair service should be called, or if you can make a home repair yourself. An AC run capacitor is a common failure, especially in climates that get extremely hot. This guide runs through a quick and easy step by step tutorial to help you troubleshoot your problem, and replace your capacitor safely.

Safety Notes

I have to say, first and foremost, if you have any doubts about working with your air conditioner, please call the professionals. Replacing a run capacitor yourself is a very easy task, but it does require you to be able to effectively shut the power off to your unit and take measures to ensure all electricity is discharged. If you are not comfortable doing this, or are worried about the task, call your local repair shop.

removing 220 volt breaker

Troubleshooting Your Air Conditioner Unit

My unit quit working as it should a few years back, and I was able to safely and effectively replace my run capacitor under the tutelage of an electrician since I was initially very nervous. This lesson has served me well and I have been able to replace the capacitor again and help others do the same.

I have always had a healthy respect for electricity, and generally leave anything having to do with it to the professionals despite there being many safe ways to work on simple electrical home repairs. If you don’t know already, getting a repair service out to your house will cost you just to have them pull into your driveway. Then you need to tack on the cost of the parts and service. Some shops are very transparent and fair about their costs upfront, and others may surprise you.

I had a very unfortunate surprise once, and it inspired me to overcome my fears of working with basic electrical components. And living in a very hot, very dry climate requires a working AC for at least 6, if not more, months out of the year.

What to Look For:

The first indication I had of my AC not running correctly the first time I did this was the lack of cold air when the unit was running. But there are a few other indicators you can watch for as well. Although these indicators may also suggest other problems, I have found them to be related to run capacitor failures. There are two main indicators that will be obvious to you that may hint at a capacitor problem.

If the unit is running, but the air doesn’t feel cold, you might have either an airflow or capacitor issue. Always change out your filters once a month to ensure unrestricted airflow. Sometimes doing this will fix the issue. If not, check your capacitor.

Also, keep in mind that an AC will blow about 20 degrees cooler than your outside temperature. You can place a thermometer over the vent to see if this is happening. If not, check the capacitor.

If your unit turns on, but you don’t hear the fan going, or it takes a moment for the fan to kick on, you need to address the issue immediately. What is happening is there is not enough power to ‘kickstart’ the fan as it should. This can tax the unit and burn it out if allowed to continually keep trying to run.

One way to check this is to take a stick and tap the fan blades. If it starts moving as it should it is almost a certainty the run capacitor didn’t have enough juice to get it going.

Why Does a Capacitor Fail?

Before you are positive your capacitor needs replacing, try resetting your entire AC unit. Power losses, power surges, and failures in the breaker can all create these issues as well. Just like any other appliance, sometimes ‘unplugging’ the unit from the grid and ‘plugging’ it back in can get everything back to normal. Simply remove the beaker from the 220v breaker panel box (which should be located near the unit), wait a few moments, and plug it back in.

Another reason why the capacitor can fail is age. Like anything else, they can wear out. One way to tell if your capacitor is worn out is the top will bubble up slightly. It also may be very rusted.

Power surges can ruin a capacitor also. They are not an expensive part overall, and I have found them to be fairly cheap in their durability. This sentiment has been echoed by AC repair shops all over the US as they find they are often replacing this part.

High temperatures might be a problem as well. They already are being heated up in their use, but if your AC unit sits in a hot area in a hot climate, you may be reducing its life expectancy.

What You Need to Replace an Air Conditioner Run Capacitor

If you are fairly certain your AC run capacitor is the problem, it is well worth replacing before having to call in a professional. These parts are inexpensive overall (about $10 to $15 each) and only take about 5 to 10 minutes to replace. Compared to a $300 service call, I am willing to give a home improvement a go first.

Correct Dual Run Capacitor for Your Unit

dual run capacitor opened and newFirst and foremost, you need to make sure you get the correct dual run capacitor to run the compressor and fan motor. If you have the owner’s manual, consult that to determine capacitor size. You can always look on the capacitor in the unit as well to see what size it is if there is an informational sticker on it (just don’t touch the capacitor).

The VAC, or voltage amp current, is an important number to pay attention to. This will be either 370 VAC or 440 VAC. You can run a 440 in place of a 370, but not vise-versa or you run the risk of larger problems. Look for part number compatibility and data stickers that provide this information.

Rubber Handled Screwdriver

You will need to remove the outer AC panel. My screws come off easily with a flathead screwdriver, but use the one that makes the job easiest for you.

Heavy Rubber Handled Pliers

I like a good, heavy-duty plastic handled plier to both discharge and remove the wires while I’m working (I’m overly cautious because, you know, electricity). I keep two types of plier handy in case I need them). The yellow and black grip pliers in the picture are my go-to for safety).

Leather Gloves and Safety Glasses

Keep in mind you are working with electricity and should have the proper personal protection equipment.

Run Capacitor Replacement: Getting Started

Before doing anything, you need to cut the power to your AC unit. I probably practice an abundance of safety measures, but it sets my mind at ease to know nothing will try to turn on while I’m working. I first turn my thermostat off so nothing tries to automatically kick on. I also want to be in control of the unit when everything is back in place so I can make sure it is working correctly.

Next, turn off the breakers in the house that connect to the AC. Again, I want to know what is connected and what is not. And I want to ensure I have full control of turning the entire system back on after the repair so I can shut it down quickly if something isn’t working right.

Once you have this under control, you can get started with the AC unit itself.

Step 1: Remove the 220 Volt Breaker

You’ll want to remove the breaker before beginning any work on your AC unit. This is a must. Do not attempt to proceed without first removing the breaker.

Step 2: Locate and Remove the Air Conditioner Panel

The panel is located on the corner of the backside of the unit facing your home. It only covers the one corner and is easy to recognize as that is where the wires and other tubing is close to that runs to a power source.

There are typically 2 to 4 screws holding the panel in place and you may need to wiggle a little as it should be snuggly up under the overhanging lip. Be sure to place your screws in a safe place until you need them again.

Step 3: Locate Run Capacitor — DO NOT TOUCH

ac capacitor with wires still attachedAs you can see, this capacitor doesn’t look like there is anything wrong with it. And I was very worried it may not be the problem. However, after replacement, the unit began working perfectly, so I may have just been starting to go bad.

Some capacitors have color-coded rings around the terminals, but not all do, so don’t assume your new one will as well. Always take a picture to see how your wires should be connected, and also to determine the placement of the new capacitor. Each capacitor terminal should be labeled as well along the top. This picture makes it hard to see, but if you zoom in you can see it etched in. The new piece below shows it more clearly.

Step 4: Discharge the Capacitor

The part is designed to hold a charge, so even though you have removed the power source, your capacitor has the potential to still have stored energy that you need to discharge. I DID NOT take a picture while I did this as it was not a practice I felt was safe. However, my picture does show the placement of my pliers after I removed the part so you can see what this will look like.

You can do this with a rubber handled screwdriver as well, but I prefer my heavy-duty pliers. To discharge, you simply need to create a bridge across the terminals to ensure discharge. You may see a small spark when you do this. Do it across each terminal at least twice to ensure all are safe. Always continue to treat the capacitor if it is charged, even after doing this as an added safety measure.

Step 5: Remove Wires and Remove the Bracket Holding the Capacitor

Do not touch run capacitor

You can either use your pliers or gloved hands to do this. I prefer the use of pliers as I can reach in and gently pull each off the terminals. Be sure not to force or yank them during this process. Allow them to rest out of the way while you unscrew your bracket and remove the old capacitor. I always lift it free with my pliers and place it on the top of the unit until I am ready to dispose of it.

Step 6: Determine How to Place the New Capacitor

Take a look at the top of your new capacitor and determine which terminal goes where so you can easily attach the wires once you have it in place. You may notice that the terminals are a bit different. That is not an issue at all since there are only 4 wires total to attach and only the C terminal ( counter- Clockwise to HERM).

Step 7: Install the New Capacitor

Be sure to screw the bracket tightly over it before connecting the wires. Use the photo you took to correctly match wires to terminals. Always double-check the wire placement to ensure everything is in the correct spot. You don’t want to short out the system by incorrectly placing them.

Step 8: Close Air Conditioner Unit

Repeat step 2 in reverse, and close up the panel. I always put the panel on without securing the screws just in case I need to get back in to make adjustments or determine if there is a larger problem than a capacitor replacement.

Step 9: Provide Electricity to the Air Conditioner Unit

Plug back in the breaker, hit the breaker switches, and turn your thermostat back on to provide electricity to the unit. Then you can test your job’s effectiveness by switching the thermostat to cool. If everything was done correctly it should power back up and begin running as long as you have the thermostat set correctly.


what you need to replace an ac run capacitor

Keep in mind that an AC not working as it should isn’t necessarily a huge, unexpected problem. Many issues surrounding a sudden lack of cold air or issues with your unit getting started are related to the run capacitor.

This is an inexpensive product that is easy to replace. Simply be sure to take safety measures surrounding electricity and ask for help from a professional if you do not feel up to the task. Let us know below how your job turned out! And, as always, please share!

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