Why Does Your AC Keep Blowing Its Capacitors?

Capacitors are a common and relatively inexpensive failure point on many central and mini-split air conditioning systems. The capacitors in your AC system help to provide the compressor with the juice it needs to start, and they also smooth the flow of power while it's in operation. Blown capacitors can stop your system from starting or cause it to shut down prematurely.

While capacitor failure isn't uncommon on older systems, it's not normal to need to replace your capacitors frequently. As with many components on a modern air conditioning system, you shouldn't often need to replace a capacitor more than once. If your system seems to be eating these critical electrical components for breakfast, it's time to conduct a deeper investigation.

Why Do Capacitors Fail?

Capacitors can fail for numerous reasons, including excessive heat or internal wear on the dielectric material between the capacitor plates. These are relatively "normal" reasons for failure, and you can expect to experience them on an air conditioner unit with many years and hours of service life under its belt.

However, capacitors can also fail when exposed to operating conditions beyond their intended usage. For example, your air conditioner's start capacitor serves a role similar to the starter battery in your car. It quickly discharges energy to get the compressor motor moving and immediately drops out of the circuit.

This quick start and rest cycle provides the capacitor with the time it needs to cool down. These capacitors cannot discharge heat rapidly, so they can fail if they remain active for too long. Likewise, frequently charging and discharging cycles can create more than the capacitor can dissipate, shortening its life and leading to premature failure.

How Can You Track Down Your Capacitor Killer?

If the capacitors on your air conditioner keep failing, your HVAC technician will need to do some detective work to track down the most likely culprit. The contactor is one common cause. This component acts as a relay, and a stuck contactor can potentially fail to disengage once the compressor motor starts.

There may also be nothing electrically wrong with the circuit. Your start capacitor will last a certain number of charge and discharge cycles before it fails. However, this service life depends on the frequency of compressor cycles. If another issue is causing your compressor to cycle rapidly, that will reduce the lifespan of your capacitor and lead to premature failures.

Other problems, including transient power surges, can potentially cause your AC capacitors to blow out more frequently than they should. With so many potential causes, it's usually best to leave these investigations to a trained HVAC technician. An experienced contractor can locate the underlying cause and fix it so your AC capacitor can go on to live a long and productive life.

For more information on air conditioning repair, contact a professional near you.