HVAC Capacitor Failure Explained

A common cause of an air conditioner failure during the summer is a failed run capacitor. This article will explain what a run capacitor is, what it does when operating correctly, how it affects your air conditioner when it fails and how to prevent the failure is the first place

A run capacitor works by storing electrical charges from a power supply and sending it to a motor to start it and run smoothly, especially when there is a lag in the power supply. Residential air conditioners mostly have dual run capacitors that start both the fan motor and the compressor. They are rated in microfarads depending on the size of the fan motor and compressor.

Why HVAC Capacitors Fail

They are susceptible over heating. When the weather gets hot, the combination of a high electrical load and high outdoor temperatures causes a much higher failure rate on these parts. Brown outs can also cause a capacitor to fail, again these are most likely to occur during very hot weather. They also fail over time with age.

As with all parts they will eventually wear out due to normal wear and tear. When a run capacitor does fail the units compressor and or fan motor will not start and the unit will not provide cooling. This will also cause the compressor and or fan motor to get electrically “hot” which is not good for these parts so if the system is experiencing a failure it should be turned off.

So what can be done to keep your AC running when the weather gets hot?

Have a pre-season tune up on your HVAC. This should include testing the capacitors to see if they are within spec’s, if not they should be replaced. If they do need to be replaced OEM capacitors seem to be made better and have a longer life than after market capacitors. There are also universal capacitors made in the USA  that will last longer. The tune up should also include a cleaning of the equipment, inspecting the other controls, testing the refrigerant levels. This will keep the system operating at optimal efficiency thus reducing the electrical load and run time of the system.