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Capacitors and Contactors: Big Deal Electric Parts of Your AC


Being an HVAC blogger dog also means knowing plenty about electrical systems. After all, electricity is what powers most home cooling systems. The standard central AC has numerous electrical parts and wires and connections and other doodads. (I know doodad is not exactly a technical term, but I think it gets the idea across.)

I want to talk to you about two electrical “doodads” that are super-duper important parts of your air conditioning system—the capacitors and the contactors. The reasons I’m bringing these ones up is that both wear down over time and may not last as long as an AC, so you may find that you need to have repairs when one of them fails.

Okay, let’s hop into these important electrical parts that keep your AC cooling your home!

The Capacitors

A capacitor usually looks like a metal cylinder (I tend to think of it as like a tall can of dog food with no label). It’s basically a battery that holds a temporary electrical charge, which it then sends to the motors in the air conditioner that power the indoor fan, the outdoor fan, and the compressor. Each motor has a separate capacitor to get it started (a start capacitor) and another one that sends periodic voltage to keep the motor running (a run capacitor).

When a capacitor fails, it means motors that won’t start or won’t continue to run. As capacitors begin to fail and lose their ability to hold an electric charge, they make clicking sounds—a good sign it’s time to call for professionals to put in a new one. Capacitors are susceptible to long heat exposure and can also start to corrode, which leads to eventual failure.

The Contactors

Think of these components as the internal on/off switches for the air conditioner. A contactor stops and starts the flow of electricity to the motors, controlling when they run as a cooling cycle starts. It’s sort of like the guards at a railroad crossing, which control when cars can pass through and when they have to stop.

A contactor can fail over time, and it can also become dirty so that it won’t be able to close and allow for voltage to flow. If the AC won’t run, or won’t stop running, a broken or dirty contactor may be the reason.

Don’t Let These Parts Shock You!

If you go online and search for air conditioning system capacitors and contractors, you’ll find that you can easily purchase them. But this doesn’t mean you should—and you absolutely shouldn’t! Trying to do a DIY replacement for capacitors or contactors is a high-risk job. You’re not only in danger of getting the wrong type of part, but you put yourself at risk of a high voltage shock if you make even a basic mistake.  You want to leave this air conditioning repair in Knoxville, TN to my friends here at Russell & Abbott, who work on these devices for a living. They know what parts your AC needs and will do the job so you have your cooling restored—and no electrical dangers!

Stay cool and don’t get shocked,