An Introduction to AC Capacitors and How to Replace Them

August 17, 2022
AC Capacitors in Rockwall, TX

If your air conditioner has difficulties turning on or won’t start at all, the problem might be caused by a bad AC capacitor. Unlike most other AC repairs, this is a problem you should be able to resolve on your own.

How an AC Capacitor Works

Capacitors are an important part of many large appliances. Your refrigerator, washing machine, dryer, and dishwasher all have capacitors as does your air conditioner. All of these appliances draw a large amount of electricity for a few seconds on startup, and this is typically more energy than their electrical circuit could provide on its own. To overcome this problem, the capacitor stores a strong electrical charge. As the unit tries to start up, the capacitor releases its stored charge to give the motor the kick-start that it needs to start smoothly.

Depending on your specific AC equipment, your system may have one or two capacitors. If there is only one capacitor, it works to supply power to the compressor motor, compressor fan motor, and forced-air blower fan motor. Some ACs have a dedicated capacitor only for the blower fan motor and another capacitor in the outdoor unit that powers the two compressor motors. If the capacitor has three wires connected to it, it supplies power to all three AC motors. If there are only two wires, it only runs the two motors in the outdoor compressor unit.

In either case, if the capacitor fails, it will cause issues when the AC compressor tries to start. You will typically hear a clicking noise coming from the unit when the capacitor starts to fail. If it completely burns out, the unit will either start and almost instantly shut off again or not run at all and make a loud humming noise whenever it attempts to start.

The Importance of Discharging the AC Capacitor

An AC capacitor is quite easy to replace. However, because it holds such a powerful charge, you can easily get shocked if you don’t discharge the energy first. This is done by first switching the AC system’s power off and then disconnecting the two capacitor terminals with the blade of a screwdriver. Make sure to always use an insulated screwdriver or else you will still get shocked when the electrical current is discharged.

How to Remove the Capacitor

The capacitor should be located within an access panel on the back of the compressor. The capacitor will resemble a can with two or three wires connected to it. After removing the panel, turn off the power to the unit and discharge the capacitor. You can then unhook the wires and remove the capacitor. When taking the wires off, make sure to note which post each wire connects to. The capacitor will have markings that identify what each of the wires is for, and you will need to make sure you connect each wire to the correct post when installing the new part.

Choosing the Right Replacement Capacitor

When shopping for a replacement capacitor, you will either need to bring the old part to the store or make note of the specifications. The three things to pay attention to are load voltage, tolerance, and capacitance. If these three specifications aren’t exactly the same as the old part, the new capacitor won’t work. Don’t worry if the replacement part is slightly larger or smaller or if it doesn’t look exactly the same. As long as it has the correct specifications, it will work.

Installing the New Capacitor

Installing the new capacitor should only take a couple of minutes. You will first need to use the mounting strap to secure the capacitor inside the access panel. Then, connect each wire to its corresponding post. This should be easy as long as you made sure to label each wire. Once it is wired up, you can test that it works by turning the power on and trying to run your AC.

If the system won’t start, you most likely don’t have it wired correctly. In this case, you’ll need to switch off the power, discharge the capacitor again, and then check that the wires are tight and in the correct spots. If everything is wired properly and the system still won’t start, it’s time to let a professional AC technician take over. Most likely, there is something other than the capacitor that is preventing the system from starting.

Reliable AC Repair and Maintenance Services

At Ken Parker Service, Inc., our technicians specialize in all types of AC repairs. Whether it is a blown capacitor or any other issue, we can get the problem quickly resolved and your AC working again as it should. Our technicians work on AC equipment from all manufacturers, and we also provide AC and heating maintenance and repair services for customers in Rockwell and throughout northeast Texas. If you are experiencing any type of AC issue, give our AC repair experts a call today.

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