How to Replace an Air Conditioner Capacitor

An HVAC technician replacing an AC capacitor.
What You'll Need
Protective gear
Voltage tester
Screwdriver with an insulated handle
New capacitor
Mounting strap

An air conditioner capacitor is an important electrical device that can cause serious system problems if it malfunctions. It is one of the most frequent causes of a problematic motor, fan, or unit as a whole, and, for this reason, knowing how to replace it yourself can save you from weeks without central air. The actual maintenance procedure is not very difficult to perform but requires careful attention and good manual skills. Here are the steps you need for a successful job.

Step 1 - Learn About Local Regulations

Get yourself well acquainted with the local health and safety regulations on the repair and maintenance of electric devices. Remember that working with electricity is a hazardous and potentially life-threatening job. If you don’t feel confident or do not fully understand any of the steps below, you had better call a professional to carry out the procedure for you instead.

Step 2 - Switch Power Off

Put on your protective gear and find the breaker that powers the condenser outside. Switch this off, and then run a quick check with a voltage tester to make sure there is no power still flowing.

Step 3 - Open Access Panel

Locate the access panel of the condenser (it usually has a label with an electrical warning on it) and open it by loosening the screws.

Step 4 - Purchase New Capacitor

Locate the capacitor just inside this panel. Typically, it is shaped like a can and should have a sticker on it. Write down its technical data (load voltage, capacitance, tolerance, etc.), and purchase a new capacitor with the same characteristics. Do not worry if the new device is of a slightly different shape or size, as this will not affect any of its operational functions. The important thing is that the new capacitor has the same performance properties.

Step 5 - Look at the Old Capacitor

Take a careful look at how the old capacitor is connected to the wires and either write down the connections or take a photo of it. You will want to hook up the new capacitor in exactly the same way.

By the way, if you have some background in electricity, you can also use the connection diagram which should be available on the inner side of the access panel.

Step 6 - Discharge the Capacitor

Take a screwdriver with an insulated handle and touch the metal end across the two terminals that stick out of the capacitor. This should discharge any energy remaining, making this part safe to handle and remove.

Step 7 - Connect the New Capacitor

Disconnect all wires from the old capacitor and attach them at their respective places on the new one. You can also carry out this step a wire at a time; disconnect each from the original air capacitor and fit it into the same place on the new device before you proceed with the next.

Once the wires are all connected, mount the new capacitor in place. If it is not stable, you may want to use a metal mounting strap to fix its position.

Step 8 - Test Connections

Double-check that the wires are connected at their respective places and test the connections by pulling slightly at each. Tighten them up, if necessary.

Step 9 - Check Condenser

Make sure the capacitor is fitted back into place, and then check the operation of the condenser by switching on the thermostat. If there are no problems, screw the access cover back in place. You are now ready to use your air conditioner once again.