It’s the hottest day of the year, and your air conditioner is making a faint humming sound, but the fan isn't spinning. You might be bracing for a multi-thousand-dollar repair bill, but the culprit is often a single, relatively inexpensive component: the .

This guide covers everything you need to know about buying the right replacement part to get your cooling system back online safely. 1. Do You Actually Need a New Capacitor?

The Ultimate Guide to Buying an HVAC Capacitor: Don’t Let a $20 Part Stall Your AC

: Using a multimeter set to capacitance ( μFmu cap F ), a healthy capacitor should read within of its rated value. 2. Reading the Label: The Specs You Must Match

When buying a replacement, you don't need to match the brand, but you match the electrical specifications. Look for these three things on your old capacitor's label: Microfarads ( μFmu cap F What are the Symptoms of a Bad AC Capacitor?

Before you head to the store, confirm that the capacitor is the problem. Capacitors typically last . Look for these "red flags":