Replacing a capacitor on your furnace, heat pump, or air conditioning system is a very easy do it yourself project. Make sure the power is disconnected before attempting this repair. A capacitor has 2 types of ratings. The first is the uf (microfarad) rating and the second is the VAC (voltage) rating. The uf rating must always be the same. The VAC rating must be at least equal to the rating. Capacitors come in oval and round styles and can be either a single capacitor or a dual capacitor. A single capacitor will have 2 distinct terminals on the top and a dual capacitor will have 3 distinct terminals on top. A single capacitor is designed to service 1 motor and a dual capacitor is designed to service 2 motors such as a condenser fan motor and a compressor. The capacitor should be flat across the top where the terminals are located. If the top is raised up or domed in any way the capacitor is bad. Another indication of a bad capacitor is oil around the outside of the capacitor. The terminals on a dual capacitor will be marked C, HERM, and FAN. It is critical that the wires are placed back on the terminal with the same markings when changing the capacitor. Switching the wires can lead to motor or compressor failure. Call or email us if you are unsure of the part needed for your capacitor repair. Capacitors are classified as either start capacitors or run capacitors. The difference between a start and run capacitor is a start capacitor is only in the circuit during startup of the motor and a run capacitor is in the circuit the entire time the motor is operating. A start capacitor has some type of device to disconnect it from the circuit as the motor approaches full speed so it is powered for a very short time. Run capacitors are more likely to fail since they are energized the entire time the motor is powered on. Link to capacitor information on our tip site.