A central air conditioner's outdoor condensing unit contains a motor that helps push gaseous refrigerant fuel into the system to start the cooling process. The motor is triggered by the indoor thermostat, which sends an electric signal that is partly intercepted by capacitors that help provide the power needed to turn on and run the motor.
The start capacitor turns on to provide an initial boost of power then cycles off. The run capacitor keeps going as long as the motor. Problems with the run capacitor can keep the motor from running properly and thwart your cooling system.
You can test the health of your run capacitor with a multi-meter that at least has AC and Ohms settings. First, you will need to cut off all electrical power to the capacitor to avoid injury and a blown fuse. Capacitors store electricity so simply turning off the power supply won't cut it with this task. You will need to discharge the capacitor before testing. Or you can simply call in an HVAC service technician to test it for you.
What You Need:
- Owner's manual for air conditioner
- Pliers, insulated
Step 1: Shut Off Power and Find the Run Capacitor
Turn off the main power to your air conditioner using the breaker box directly next to the unit or your indoor primary breaker box. Use your owner's manual to determine where your run capacitor is located. The capacitor is usually directly on the motor or mounted to an interior wall nearby.
If you don't know how to open your condensing unit, you can also find that information in the manual. Typically, you only need to look for the fasteners that connect the grated case to the main body and unscrew or unlatch those fasteners.
Step 2: Prep the Run Capacitor
Locate the run capacitor and make note of the wires sticking out of the terminal connects. Use a pair of insulated pliers – the insulation is vital to keep yourself from getting electrocuted when metal touches wires – to remove the wires. Carefully drape the wires nearby for easy reattachment if your capacitor ends up testing healthy.
Step 3: Discharge the Run Capacitor
Some guides recommend discharging the run capacitor using a screwdriver with an insulated handle. But that technique can end up blowing a fuse and destroying a capacitor that might have been healthy before the discharging.
Use your multi-meter for a safer discharge process. Set the multi-meter to read in AC and attach the meter's own wires to the ends of the terminal connections on the capacitor. Wait for the AC reading to slowly fall down to zero to know that the capacitor is fully discharged.
You can proceed with testing the run capacitor after the discharge is complete. For more information, talk to an HVAC service.