Many homeowners choose to call an HVAC technician as soon as their central air conditioner breaks down. However, there is one problem that DIY-oriented homeowners can repair on their own before calling a professional: a faulty compressor motor capacitor. Here is more info on the steps you can take to diagnose and replace the capacitor in your central air conditioner.
Diagnosing Capacitor Problems
Before you go to the trouble of opening your air conditioner to replace the capacitor, you should look for common symptoms of capacitor failure, such as a burning smell or smoke coming from the air conditioner.
There is a simple test you can do to determine if a faulty capacitor is the problem. With the thermostat set to cool, slide a stick through the fan grate on your air conditioner, give the fan a nudge, and quickly pull the stick back out.
If the fan keeps spinning on its own after you push it, it is very likely that you have a faulty capacitor. This is because the job the capacitor does for your air conditioner is very similar to what the starter does for your car. The capacitor gives a short jolt of electricity to the fan motor to get it running when you first turn on your air conditioner. If the capacitor is faulty, your air conditioner will hum but the fan will not move, so no cold air will come into your home.
Accessing and Discharging the Capacitor
Once you have determined that the capacitor is the likely cause of the problem, you can start on removing the faulty part. First, turn off the thermostat and cut the power to your air conditioner by pulling the fuses out of the double breaker next to the unit. Next, use a screwdriver to remove the service panel and reveal the capacitor and wiring. On most air conditioner models, the service panel is on the side and has an electrical safety warning label.
Even with the power to your air conditioner turned off, the capacitor will still hold a potentially harmful charge. To safely replace the capacitor, you will need to use a screwdriver with an insulated handle to discharge it before attempting to remove it from the air conditioner. Most capacitors will have two terminals on top, and can be discharged by bridging the leads with the metal part of the screwdriver. Be sure that you are only touching the insulated handle when you bridge the terminals to avoid injury.
Some capacitors have three terminals marked "C" for common, "Fan" for the fan wire, and "Herm" for the hermetic motor wire. To discharge these capacitors, first bridge the "C" terminal and "Fan" terminal, followed by the "C" terminal and "Herm" terminal.
Replacing the Capacitor
You are ready to remove the old capacitor after you have discharged it, but before you do you should take note of how it is wired. Writing down the colors of the wires that are attached to each terminal is one way to do this. You could also take a photo of the installed capacitor as long as you can clearly see which wires are attached to which terminals.
To remove the capacitor, first use needle-nose pliers to remove the clips holding each wire in place. Then use a screwdriver to loosen the screw that is securing the capacitor's mounting bracket. Take the old capacitor with you to a local appliance store so you can find exactly the same model to replace it with.
Installing the new capacitor is as simple as re-securing it with the mounting bracket, reconnecting the wires according to your notes, replacing the service panel, and reinstalling the fuses in the double breaker. With the new capacitor in place, you should find that your air conditioner fan starts on its own and your home has cool, comfortable air once again.