Use extreme caution when working with capacitors. They hold high amounts of charge even if the power is turned off.


If your central air conditioner is not working at all, it’s likely that the problem is the outdoor compressor’s capacitor or contactor. The capacitor, sometimes called a “run capacitor,” starts the condenser and the fan in the outdoor unit. If the capacitor fails, the air conditioner won’t run.

What are the signs of a failed AC capacitor or contactor?

The most common sign of a failed capacitor is a clicking sound followed by a buzz or hum. Although you can sometimes start the compressor fan spinning (clockwise) by pushing it with a thin stick or long screwdriver poked through the grille, this is a temporary fix. You’re better off replacing the capacitor.


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Should you do it yourself?


但是,如果您没有必要的技能或工具,请将这些维修留给HVAC维修专业人士。To have these professionally replaced typically costs from $90 to $450.



在A / C单元上打开电气盖之前,be sure to shut off all power to the compressor unit and the indoor furnace or air handler, and verify that it is off请注意,这可能意味着切断用于炉子和空气处理器的断路器,然后在压缩机附近,将断开块(或将220伏动力关闭)拔出到室外压缩机。

expert advice for AC repair当您最需要时,电容器通常会失败。当您探索AC单元的压缩机以查看电容器时,请注意确切的类型和规格。无论您的电容器是否发生故障,订单更换Amazonto keep on hand for when you need it.

To work safely and effectively, please watch the next three videos below before beginning.

Beware: An AC capacitor stores voltage and could shock you! Do not touch the terminals.在处理它之前,如下所示放电电容器。

To get to the capacitor, remove the compressor unit’s access panel as shown in the capacitor testing and replacement videos below.


To discharge a run capacitor, wear safety glasses and gloves. Hold the handle of an insulated electrical screwdriver (not touching the metal!), and use the screwdriver’s blade to bridge across the terminals on the capacitor. Be prepared for a spark!




用一个数字万用表设置为“电容”,将一个引线放在公共(C)终端上,另一个引线在其他两个端子中的一个上。仪表应显示一个数字 - 不是“ol”,表示短暂的。

Here is a video that shows more precisely how to test and replace a capacitor.

提示:快速数字线之前的照片e disconnecting them so you know where to replace them.



请注意:如果您没有清楚地了解如何正确安全地更换电容,请致电HVAC Pro。

Still not working? Check and, if necessary, clean or replace the AC contactor. Also read “空调不吹空气,“ 以下。

How to Check and Replace an AC Contactor


If the AC doesn’t run or hum but you hear it clicking, the contactor probably needs to be replaced.

Before working on this,be sure to shut off all power to the compressor unit and the indoor furnace or air handler, and verify that the power is off


The following video shows you how to replace the contactor. We recommend that you take a photo of where the wires are connected to the contactor before removing them so you can see where they go on the new contactor.

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关于Don Vandervort.
Don Vandervort has developed his expertise for more than 30 years, as Building Editor for Sunset Books, Senior Editor at Home Magazine, author of more than 30 home improvement books, and writer of countless magazine articles. He appeared for 3 seasons on HGTV’s “The Fix,” and served as MSN’s home expert for several years. Don founded HomeTips in 1996.阅读更多关于Don Vandervort的信息