How to install a hard start capacitor?

A capacitor is a storage device for electrical power or voltage. Capacitors come in all shapes and sizes, so it is important that you consult an electronic specialist to make sure you purchase the one that is right for your circuit. 

Most electrical problems in air conditioning systems are in the compressors and their relays or motor overload switches.In a single phase (common residential A/C) compressor you can verify with an ohmmeter whether or not the A/C compressor is bad. The capacitor acts as a storage tank for electrical power. The start capacitor can go in a number of places in your system. There is only a negligible difference in effectiveness no matter where you place it, but nearest the components that are struggling to get power is considered best. Although you are installing the capacitor to keep up with the extra power that is being pulled from accessories such as an upgraded stereo system, you have to remember that the capacitor is like a storage tank for power that supplements the whole system. By putting it close to the parts that are not getting sufficient power you allow it to supply power to those parts with minimal loss do to the extra resistance of a long wire.

Once the capacitor is properly installed, the circuit can be used. A charged capacitor can release a large amount of energy very quickly. This can be quite dangerous. You should always handle electrical components with care. When installing a capacitor it is important to use caution, as a capacitor can easily shock you. Make sure that it is installed in such a way that it cannot accidentally touch anyone. 

Here are some sample capacitor installation instructions for adding a motor starter capacitor to an air conditioning compressor motor - taken from the product package for a relay and start capacitor intended for use on a refrigerator or freezer. Similar starter capacitors are available for air conditioning compressors:

1.Remove the power supply cord from the electrical outlet - in other words, be absolutely certain that electrical power has been turned off to the equipment being serviced.

2.Remove the old starting relay, leaving the old overload protection in place.

3.Push the wire with the one single pin terminal onto the "start" terminal of the air conditioning compressor. (See the wiring diagram above).

4.Push the other wire with the pin terminal onto the "run" terminal of the air conditioning compressor.

5.Connect the line from the old starting relay to the spade terminal on the "run" wire (insulating sleeve).

6.Restore electrical power

When testing a compressor, one must discharge the capacitor first! It'll otherwise have enough power stored on it to be at least very painful. Some systems will automatically discharge the capacitor, but shorting its leads [to ground] with a screwdriver (after verifying that the power's off) is a safe way to ensure that you won't get shocked. Motor starting capacitors can hold a charge for days! Also, the capacitor may be defective if the compressor hums but does not start. Visual inspection may reveal it to be bulged, or have a blown out safety plug.