Overview

In this blog, the HVAC experts at Custom Air Systems explain the most common signs of a failing AC compressor, what causes these issues, and what you can do to prevent total system breakdown.

Highlights

Introduction

The AC compressor is often referred to as the heart of your air conditioning system. It compresses refrigerant and helps move it through the system to remove heat from inside your home. If your air conditioner isn’t cooling like it used to, the culprit could be the compressor.

This essential component drives the entire cooling process, and when it starts to fail, your comfort is at risk. Let’s explore the red flags of a failing AC compressor and how you should respond.

Reduced Cooling Performance

One of the first signs of compressor trouble is a noticeable drop in cooling capacity. If your AC seems to be running constantly but the air inside your home feels warmer than usual, something may be interfering with refrigerant circulation.

A weak or failing compressor may not be able to adequately pressurize the refrigerant. Without proper pressure, heat exchange slows down, and your system can no longer maintain the temperature set on your thermostat.

Here’s what to watch for:

  • Rooms feel warm even with the AC running.
  • Airflow seems normal, but the temperature is off.
  • Thermostat settings have little effect.

While these symptoms could also indicate other problems, such as refrigerant leaks or a dirty evaporator coil, the compressor is a likely suspect when performance drops across the entire system. When any of these issues occur, it's important to seek professional air conditioning repair promptly to prevent the issue from worsening.

Strange Noises From the Outdoor Unit

Your AC compressor lives in the outdoor unit (the condenser). When it begins to fail, you might hear noises that were never present before. These sounds are often early clues that mechanical parts inside the compressor are struggling.

Sounds that signal trouble include:

  • Rattling: Loose parts or failing motor mounts
  • Grinding: Worn bearings or internal damage
  • Screeching: A pressure imbalance or a slipping belt from a seized compressor
  • Clicking or buzzing: Electrical issues sometimes caused by a hard-starting compressor

These sounds usually get worse over time, especially when the compressor turns on or off. If you hear anything unusual coming from your outdoor unit, it’s a good idea to shut it off and call an HVAC technician.

Hard Starts or No Start at All

A healthy compressor starts smoothly. If your unit struggles to turn on or won’t start at all, you may be dealing with a compressor failure or an electrical issue related to it.

In technical terms, a hard start occurs when the compressor has difficulty overcoming internal pressure and resistance. You might hear a stutter, delay, or series of clicking sounds when the unit powers on. Eventually, a hard-starting compressor can overheat and stop working entirely.

Signs of hard starts include:

  • The outdoor unit hesitates or stutters when turning on.
  • It shuts off suddenly after a few seconds.
  • You notice lights dimming when the AC starts (a sign of electrical strain).

Circuit Breaker Keeps Tripping

Frequent circuit breaker trips are another sign that your compressor may be on its last legs. This usually indicates that the unit is drawing too much power, either because of electrical faults or internal stress, often on the compressor.

You should never repeatedly reset your breaker without diagnosing the issue. Overloading the circuit can damage other electrical components and create a fire hazard.

Common causes include:

  • A short-circuit in the compressor windings
  • Locked rotor drawing excessive amperage
  • Faulty capacitor or contactor
  • Issues with the fan motor or wiring

While there are other potential causes, the compressor is often the root of the problem when power overloads happen consistently.

Shaking or Vibrating When the Unit Starts

Your air conditioner should start up with minimal movement. If your unit noticeably vibrates or shakes when the compressor kicks in, that's often a symptom of internal failure.

This shaking can result from the aforementioned condition, hard starting, in which the compressor motor struggles to start due to internal damage or electrical resistance.

Over time, repeated hard starts can damage mounting brackets and other components, escalating the repair costs. It also makes your system noisier and less efficient.

Warm Air Blowing From the Vents

If you feel warm air instead of cool air coming from your vents, it could be a sign that the compressor is failing to circulate refrigerant properly.

This problem might be intermittent at first, with the air feeling warm during peak hours but cooling down at night. That’s because the compressor may only work under low demand. As the issue worsens, you'll get warm air all the time.

There are other possibilities, though, which could include:

  • Low refrigerant levels (from a leak)
  • A clogged or dirty condenser coil
  • A malfunctioning thermostat

An HVAC technician can run tests to determine whether the compressor is causing the issue or if another part of the system is at fault.

Refrigerant Leaks Around the Outdoor Unit

While the compressor doesn’t generate refrigerant leaks on its own, its seals and fittings can deteriorate over time. A refrigerant leak near the outdoor unit could indicate a compressor with failing seals or a cracked housing.

Low refrigerant levels strain the compressor, often leading to overheating and failure. If you see oily spots or detect a chemical smell around the unit, call a technician immediately. Refrigerant leaks can be harmful to both your system and the environment.

Compressor Clutch Not Engaging

Some AC systems use a clutch mechanism to engage the compressor. If this clutch fails to engage, the compressor won’t run, and the system won’t cool.

This is more common in automotive systems, but a few residential AC models also use similar technology. If the compressor clutch is the problem, it can often be replaced without changing the entire unit.

Rising Energy Bills

If your power bill is steadily increasing without a change in usage habits, your AC system may be working harder than necessary. A failing compressor has to draw more electricity to achieve the same results. This inefficiency puts stress on your entire HVAC system, including your blower motor and thermostat. If left unresolved, the added workload can shorten the lifespan of other components.

What Causes AC Compressor Failure?

Understanding what leads to compressor failure can help you take preventive action. Most compressor issues don’t appear out of nowhere. In fact, they build up over time due to system strain or neglect.

Common causes include:

  • Lack of maintenance: Dirty coils, clogged filters, and poor airflow all increase system pressure.
  • Refrigerant issues: Overcharging or undercharging affects pressure balance and efficiency.
  • Electrical problems: Power surges, failed capacitors, or loose connections damage internal windings.
  • Contamination: Moisture, dirt, or air inside the refrigerant lines causes corrosion and clogs.
  • Improper installation: Incorrectly sized systems or faulty setups lead to long-term stress.

Can a Failing AC Compressor Be Repaired?

In some cases, it can be. However, compressor repair is often complex, and most HVAC companies recommend replacement over repair due to the high labor costs and risks of recurring issues. That said, if the failure is caused by something external, such as a faulty capacitor or relay, you might avoid a full replacement. The key is prompt, accurate diagnosis.

If your system is under warranty, the manufacturer may cover the compressor replacement, though labor is sometimes excluded. Always check your warranty status before proceeding.

When To Replace Your Entire AC System

If your compressor is beyond repair or fails in an older system (10+ years), replacing the entire AC unit might make more financial sense. Installing a new compressor in an aging system can lead to mismatches in efficiency and new problems down the road.

Consider a complete replacement if:

  • Your system uses R-22 refrigerant, which is now banned.
  • Multiple components have shown signs of failure.
  • Repair costs are 50% or more of the price of a new system.
  • The unit struggles to maintain a consistent temperature.
  • You’re facing repeated service calls for the same issue.
  • Your system is undersized or outdated for your current home size and usage.

A new, energy-efficient unit will not only resolve your cooling problems but also help lower your energy bills over time. It also adds value to your property and reduces the likelihood of emergency HVAC repairs during peak seasons.

Schedule an AC Inspection With Our HVAC Repair Team

The AC compressor is one of the most important and expensive parts of your cooling system. Knowing the early warning signs of compressor failure can save you thousands of dollars in emergency repairs or replacements.

If you notice poor cooling, strange noises, tripped breakers, or any of the other signs listed above, don’t wait. Contact Custom Air Systems, a trusted HVAC professional specializing in air conditioning repairs, to inspect your system and diagnose the issue. Reach us at (281) 489-1830 today to schedule an AC diagnostic.