The 10 Most Common AC Parts that Fail and Why

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Last Revised: 5/30/25

Is your AC struggling to keep up with rising temps – or not turning on at all? Are you worried about costly breakdowns during the hottest days of the year?

Troubleshooting AC issues can feel overwhelming, but the truth is that most failures trace back to just a handful of components. Once you know what to look for, they’re easier to catch than you think.

At Mattioni, we’ve helped thousands of homeowners spot early warning signs and prevent major system failures. In this article, you’ll learn about the 10 most common AC parts that fail, how to recognize the symptoms, and how to prevent costly repairs.

Let’s jump in with our first two components.

1. Capacitors

What Fails: Capacitors store and deliver energy to start and run your AC. Over time, they degrade due to heat, age, or power surges.
Impact on Your AC: A failing capacitor can prevent your AC from starting, or it may cause it to shut down abruptly. You may hear a humming noise or notice the fan isn’t spinning even when the system is on. You may experience inconsistent cooling, higher energy use, and more strain on other parts, like the compressor.
How to Fix It: Capacitors are relatively inexpensive but should be replaced only by a licensed technician due to the electrical hazards involved. HVAC professionals will test capacitor strength during routine maintenance to catch the issue early.

2. Contactors

What Fails: Contactors are electrical switches that control the flow of electricity to major AC components like the compressor and condenser fan motor. Over time, contact points can burn out from electrical arcing and high current loads.
Impact on Your AC: A bad contactor can prevent the system from starting or cause it to run intermittently. You might hear clicking sounds or notice the outdoor unit failing to turn on.
How to Fix It: Contactors are affordable parts but replacing them should be left to licensed professionals due to the electrical risks. Regular inspections can catch wear early.

3. Compressors

What Fails: The compressor is the heart of your AC system, pumping refrigerant between the indoor evaporator coil and outdoor condenser coil. It can fail due to overheating, low refrigerant, or electrical issues.
Impact on Your AC: If the compressor fails, your AC can’t cool your home. Replacing a compressor can be expensive, and if your system is over 10 years old, it may be more cost-effective to replace the entire unit.
How to Fix It: Early diagnosis is key. An HVAC technician will assess whether a repair or replacement makes more sense based on the age and condition of the unit.

4. Refrigerant Leaks/Low Refrigerant

What Fails: Refrigerant lines can develop leaks due to corrosion, vibration, or factory defects. Low refrigerant reduces the system’s efficiency and cooling ability
Impact on Your AC: You may notice reduced cooling, ice on the evaporator coil, or hissing noises. Prolonged operation on low refrigerant can damage the compressor.
How to Fix It: A technician must locate and repair the leak before recharging the system with the correct refrigerant. This requires EPA-certified handling.

5. The Evaporator Coil

What Fails: The evaporator coil absorbs heat from indoor air, which is then released outdoors. Freezing is a common issue with this critical component, which can be due to airflow issues, low refrigerant, corrosion, or leaks.
Impact on Your AC: A frozen or leaking indoor evaporator coil means your AC won’t cool properly. You may also see water dripping or pooling near your indoor unit.
How to Fix It: Depending on the severity of the issue, the coil may need cleaning, defrosting, or replacement. Preventative care keeps coils clean and functioning efficiently.

6. The Condenser Coil

What Fails: Located in the outdoor unit, the condenser coil releases heat removed from your home’s indoor air. Dirt, debris, and corrosion are common culprits that can cause this component to overheat, reducing performance and efficiency.
Impact on Your AC: When the condenser coil is dirty, damaged, or overheating, your system is forced to work harder and therefore cools less effectively. This can lead to increased energy bills, inconsistent temperatures, and a shorter system lifespan.
How to Fix It: If your condenser coil is dirty or damaged, professional cleaning or repair is the best solution. Technicians may also check for bent fins or replace the coil if corroded beyond repair.

7. Blower Motors

What Fails: The blower motor circulates cooled air throughout your home’s ductwork and into your living spaces. Failure can result from debris buildup, bad bearings, overheating, or electrical issues.
Impact on Your AC: If the blower motor fails, your system may run but no longer have the airflow needed to deliver air through the vents. This can also strain other components like the evaporator coil.
How to Fix It: Blower motors can often be repaired or replaced, depending on the severity of the issue. Regular maintenance can help prevent overheating and prolong the lifespan of your blower motor.

8. Condensate Drain Lines

What Fails: Condensate drain lines carry away the moisture that’s been removed from your indoor air. Over time, debris, mold, and algae can clog the line.
Impact on Your AC: A clogged drain line can cause water backup and trigger the system’s safety switch, shutting down the AC. It may also lead to water damage around the air handler.
How to Fix It: Clearing the line is a simple maintenance task that includes flushing with water or vinegar. Professional tune-ups ensure this is handled regularly.

9. Air Filters

What Fails: Filters don’t exactly “fail,” but when neglected, they become clogged with dust and restrict airflow.
Impact on Your AC: Reduced airflow from a dirty air filter can set off a domino effect of problems, including excess strain on the system, short cycling, and eventually a frozen evaporator coil.
How to Fix It: Check and replace your air filter every 1-2 months, depending on usage, pets, or allergy concerns.

10. Circuit Breakers

What Fails: Air conditioners draw a lot of power. Frequent tripping may signal an electrical fault or overloaded circuit.
Impact on Your AC: Repeated tripping prevents your AC from running and may signal a serious issue like a short or bad capacitor.
How to Fix It: A technician will diagnose the root cause. Don’t just reset the breaker repeatedly – this could damage your system or create fire risk.

Signs Your AC Might Be in Trouble

How do you know if a single part is failing – or if something more serious is going on? Most air conditioner issues don’t start with a dramatic shutdown. They begin with small changes in performance that homeowners often overlook. Recognizing the early signs of trouble can help prevent major damage and costly repairs.

Common warning signs that you’re overdue for a tune-up include:

Warm air from your vents
Frequent on/off cycling (short cycling)
Unusual noises
Weak airflow
Water around the unit
Rising energy bills

If you notice any of these signs, it’s time for a professional inspection. These symptoms often point to underlying issues – and catching them early can prevent extensive damage.

How Regular Maintenance Prevents Most AC Failures

Most of these issues are preventable (or at least detectable early) with regular AC maintenance. Seasonal tune-ups from a trusted professional can catch worn components, clean critical parts, and ensure your system runs efficiently.

Preventative care can extend your AC’s life by years and greatly reduce the risk of emergency breakdowns during peak summer heat.

Stay Cool and Confident with Mattioni

If you’ve ever dealt with an underperforming AC, you know how quickly comfort can turn into chaos. Now that you understand the 10 parts most likely to fail – and the warning signs – you’re in a stronger position to take action.

At Mattioni, we’ve spent over 75 years helping homeowners throughout our community stay cool and confident. Whether it’s a simple filter replacement or a full-system diagnosis, we’re here to help.

Don’t wait until your AC breaks down – your next step is to schedule your AC tune-up online or by calling our friendly staff at (610) 400-8510.