AC Capacitor Failure: Signs, Costs & What Charlotte Homeowners Need to Know

The capacitor is one of the most common AC parts to fail—and thankfully one of the cheapest to replace. It's a small cylinder that stores electrical energy and provides the boost needed to start your compressor and fan motors. When it fails, your AC typically won't start or will struggle to run.

Here's everything you need to know about capacitor problems: how to recognize them, what causes failure, and what repair will cost.

What Does an AC Capacitor Do?

Think of a capacitor like a battery that charges and discharges quickly. Your AC has two types:

• Start capacitor: Provides the initial power surge to start the compressor
• Run capacitor: Keeps the motor running smoothly once started

Many modern systems use a "dual run capacitor" that handles both the compressor and condenser fan motor. When this single part fails, multiple components stop working.

Signs of a Bad AC Capacitor

1. AC Hums But Won't Start

This is the classic capacitor failure symptom. You hear the motor trying to start (humming sound) but it can't get going. Without the capacitor's electrical boost, the motor doesn't have enough power to turn.

2. AC Struggles to Start (Hard Starting)

Before complete failure, a weak capacitor causes "hard starting"—the system hesitates or struggles before turning on. You might hear clicking or stuttering before the compressor finally kicks in.

3. Random Shutoffs

A failing capacitor may let the AC start but not keep it running. If your system shuts off randomly or trips the breaker, capacitor failure is a possible cause.

4. AC Fan Not Spinning

If the outdoor unit hums but the fan doesn't spin, the fan motor capacitor has likely failed. Sometimes you can get the fan started by spinning it manually with a stick (with power off!)—a temporary sign the capacitor is bad.

5. Clicking Sounds from Outdoor Unit

Repeated clicking from the outdoor unit when the AC is trying to start indicates the contactor is engaging but the capacitor can't provide enough power to start the motor.

6. Swollen or Leaking Capacitor

A visual inspection can confirm capacitor failure. A bulging top, oil leaking from the case, or burn marks are definitive signs the capacitor has failed.

What Causes Capacitor Failure?

• Age – Capacitors typically last 10-20 years; they wear out over time
• Heat exposure – Charlotte's summer heat accelerates degradation
• Power surges – Lightning and electrical spikes damage capacitors
• Short cycling – Frequent on/off cycling from oversized systems stresses capacitors
• Voltage issues – Operating outside rated voltage range causes premature failure
• Physical damage – Debris, lawn equipment, or pests can damage capacitors

In Charlotte, the combination of heat and summer electrical storms makes capacitor failure especially common. We replace more capacitors in July and August than any other months.

Capacitor Repair Cost

Capacitor replacement costs $200-$300, which includes parts, labor, and a full system diagnostic. This makes it one of the most affordable AC repairs—and at Kodiak, there are no surprise fees or add-ons.

Why You Shouldn't Ignore Capacitor Problems

A weak capacitor doesn't just affect startup—it can cause serious damage:

• Compressor damage – Hard starting stresses the compressor windings; repeated hard starts can burn out a $1,500-$3,500 compressor
• Higher energy bills – A struggling motor draws more electricity
• Overheating – Motors working harder generate excess heat, shortening lifespan
• Complete system failure – What starts as a $200-$300 repair can become a $1,500-$3,500 repair if ignored

Can You Replace a Capacitor Yourself?

Technically, yes—capacitors are relatively simple to replace. However, we don't recommend DIY capacitor replacement because:

• Electrical hazard – Capacitors hold charge even with power off
• Correct rating required – Wrong capacitor damages motors
• Diagnosis needed – Symptoms might indicate other problems
• Warranty concerns – DIY work may void equipment warranty

Given the low repair cost, professional replacement is the smart choice for most homeowners.

How to Prevent Capacitor Failure

Frequently Asked Questions