Think of a capacitor like a battery that gives your HVAC system a jump-start. It stores and quickly releases energy to help power up important components like:

  • The compressor (which pumps refrigerant)

  • The blower motor (which moves air through your home)

  • The fan motor (especially in your outdoor unit)

Without a working capacitor, your HVAC system might struggle to start—or not run at all.

There are two main types you'll usually find:

  • Start capacitors – help components get going

  • Run capacitors – keep them running efficiently

If you're in Philly dealing with those sticky July heat waves or one of our unexpected spring cold snaps, you definitelywant your system to fire up without hesitation.

Why Do Capacitors Fail?

Capacitors aren’t made to last forever. Here’s what usually does them in:

  • Age – They naturally wear out over time.

  • Heat – Hot summers (hello, Philly in August!) can degrade them faster.

  • Power surges – Sudden voltage spikes can fry them.

  • Poor maintenance – Dirt, debris, or electrical issues can cause extra strain.

How Do You Know If Yours Is Bad?

Some telltale signs:

  • Your AC is humming but not starting

  • The fan runs but the air isn’t cool

  • It starts up slowly or shuts off unexpectedly

  • You hear a clicking or buzzing sound from the unit

Heads up: A failed capacitor can cause strain on other parts of your HVAC system. So, letting it go for too long could turn a simple fix into a costly repair.

Can You Replace It Yourself?

If you’re handy and know how to safely handle electrical parts (and we do mean safely—capacitors can store dangerous charges even after they’re off), it’s technically a doable DIY job. But for most folks, this is one of those “know when to call a pro” moments.

It involves:

  • Turning off all power to the unit (not just the thermostat!)

  • Discharging the capacitor safely

  • Identifying the exact right size and type for your system

And if you install the wrong one? You could damage your compressor or fan motor.

When to Call for Help

If you're not totally confident or just don’t want to deal with high-voltage parts on a hot summer afternoon, call in a professional. A local HVAC pro—like the folks at McCorry Comfort, who know their way around Philly’s older rowhomes and newer builds—can get you fixed up fast.

Bottom line: The capacitor may be small, but it's a mighty piece of your HVAC puzzle. When it fails, your whole system can go down. Replacing it promptly helps keep your home cool, your electric bill lower, and your AC stress-free.