Can A New Start Capacitor Fail?

Start capacitor failures are a relatively common reason for HVAC service calls. Your start capacitor is part of the outdoor half of your home's air conditioning system. This simple electrical component lives in your condenser unit and provides the initial jolt necessary to start your compressor. In a sense, the start capacitor serves a similar function to the battery in your car. 

A faulty capacitor will either prevent your compressor from running or cause it to struggle to start. If you can hear your compressor struggling to turn on with each cycle, there's a good chance your capacitor will fail and eventually stop working. However, what if you've recently replaced your start capacitor? Is it possible for a relatively new capacitor to continue to cause trouble for your system?

Understanding Capacitor Failures

Like most electrical components, heat is the number one enemy of your start capacitor. However, this fact leads to common misconceptions about why these components fail. While start capacitors may fail on hot days, a good unit can withstand normal outdoor temperatures. If a hot day kills your start capacitor, it was likely already on its last legs.

Instead, the most likely culprit for an otherwise "healthy" capacitor failing is an abnormally large amount of heat. There are two primary reasons why the capacitor in your outdoor unit might experience an excessive amount of heat and fail: excess compressor current draw and excess capacitor run time.

The first scenario occurs most often due to other problems with the AC system. Clogged-up condenser coils, a faulty condenser fan, poor indoor airflow, or a refrigerant leak can all overwork the compressor and cause it to draw too much current. On the other hand, the second case occurs when there's a problem with the capacitor relay that causes it to remain in the circuit for too long.

Avoiding Repeat Capacitor Failures

At first glance, capacitor problems seem relatively easy to solve. You can often remove the service panel from your outdoor unit and quickly inspect or test the capacitor to determine if it's faulty. Unfortunately, this approach can lead to false confidence. Replacing your faulty capacitor may get your system running, only for it to fail days, weeks, or months later.

While capacitors aren't expensive, repeatedly replacing them is a bad idea. Unless you know your capacitor is very old, you'll want to confirm that it didn't fail due to another problem. If you aren't comfortable performing this work yourself, it's time to call in a professional. An expert can check your system for underlying issues, so your new capacitor doesn't fail just as quickly as your old one.

Contact a local air conditioning repair service to learn more.