Why Your AC Compressor Isn’t Working: Common Causes and Next Steps

Your AC compressor is not working, and it’s an especially hot day in Denver. Because this frustrating problem can be due to multiple causes, it’s important to figure out why it is happening. While there are some checks you can do on your own, all mechanical, electrical, and refrigerant-related work should be left to a Comfort Specialist from Elkhorn Heating, Air Conditioning, Plumbing & Electrical.

What Homeowners Mean When They Say the Compressor Is Not Working 

Often, we’ll get emergency calls about AC compressors not working. This frequently occurs if the outside AC unit is humming and not cooling. The unit may also produce clicking noises, trip the breaker frequently, or remain completely silent. 

Many different issues can look like an AC compressor failure. These problems can be caused by other faulty components as well. Because of this, it’s always a good idea to have a professional inspect your unit if you suspect compressor malfunctions.

Safe First Checks Before You Call 

If you think your AC compressor is not working, there are a few basic checks you can perform to troubleshoot the malfunction.

Check 1: Confirm Your Thermostat Settings

If the thermostat isn’t set to “cool” mode or the setpoint is too high, it will seem like your AC compressor is not turning on.

Check 2: Inspect the Air Filter

Routine maintenance is integral for preventing airflow problems and premature wear. Ideally, the air filter should be replaced every 30 to 90 days. If it is clogged from intense AC use, it needs to be replaced earlier. For complimentary tune-ups and springtime performance inspections, Denver homeowners can check out our Whole Home Comfort Plan.

Check 3: Verify the Breaker Is On

Many outdoor units use a separate breaker. If this breaker trips, you will still feel airflow inside. Because the outdoor unit isn’t on, the airflow will feel warm. 

You can troubleshoot this issue by turning the breaker on again. However, you should immediately schedule repairs if you notice the breaker tripping right away.

Check 4: Inspect the Condenser Unit

Check your condenser unit for debris or signs of obvious damage. If it is dirty, you can use a gentle stream of water from your hose to clean the unit. Then, remove any debris and plant matter that is around the unit.

Check 5: Listen for Unusual Sounds and Brief Starts

Pay attention to any humming or continuous clicking sounds. You should also note if the AC briefly starts up before shutting down again.

If your Denver AC compressor is not starting, you should never open panels or reset the breaker repeatedly. For the safety of your home and family, electrical and refrigerant repairs should always be left to the experts.

Symptom-by-Symptom Troubleshooting Guide

Over the years, we’ve dealt with all types of AC symptoms. The following are some of the most common compressor-related symptoms and when you should call for help.

Symptom: Unit Will Not Start at All

Possible Causes: This issue can occur if there is a problem with your capacitor, contactor, wiring, or breaker. 

When To Get Help: You should call for help if the unit won’t switch on after you reset the breaker once.

Symptom: Fan Runs but No Cooling

Possible Causes: You may notice this type of problem if you have a faulty compressor, control problem, or refrigerant issue. 

When To Get Help: If there is a hissing noise or your unit keeps blowing warm air, it’s time to call for help.

Symptom: Clicking or Humming 

Possible Causes: A clicking or humming sound may occur if you are dealing with a locked rotor scenario or failed start components. Often, homeowners will note that an AC compressor clicks and then stops if there is a problem with the capacitor, motor, refrigerant levels, or contactor. 

When To Get Help: If your outdoor unit is on when your indoor fan is off, or you smell a burning odor, you should schedule repairs right away.

Symptom: Breaker Trips When Cooling Starts

Possible Causes: You may notice this problem if there is an electrical overload or a shorted component. However, this symptom can also occur when your compressor is strained.

When To Get Help: When the breaker trips more than once, you should call for help because this means that there is a severe electrical problem involved.

The Most Common Causes We See in the Field 

At Elkhorn Heating, Air Conditioning, Plumbing & Electrical, we often get called about common issues that mimic AC compressor failure. Our compressor calls result in a range of different problem identifications.

• Failed capacitor
• Dirty coils
• Faulty contactor
• Airflow restrictions
• Refrigerant leaks that are straining the compressor
• Electrical malfunctions from panels, disconnects, or wiring

Sometimes, the main issue is truly the compressor. In general, we’re more likely to see true compressor failure in older systems than in newer ones.

When To Shut the System Off and Call Right Away 

When your Littleton AC is not cooling, troubleshooting is normally the first step. However, you should immediately turn off your unit and get help if you notice any of the following signs.

• Repeatedly tripped breakers
• Burning odors
• Loud metal-on-metal noises
• Visible electrical damage
• Hard-start behavior
• Any time you have vulnerable family members and no cooling options during heat waves

Whether you need same-day repairs or an AC installation, our Comfort Specialists are committed to upfront pricing and no hidden fees. For a more in-depth look at common compressor warning signs and how to decide between replacing or repairing your AC, check out our compressor troubleshooting guide.

Frequently Asked Questions

Does this always mean the compressor is bad? 

Not always. While it may seem like the compressor is bad, similar symptoms can occur if you have a problem with your contactor, capacitor, or thermostat.

Should I keep resetting the breaker? 

When your breaker trips, note it and reset it. If your compressor breaker keeps tripping, your AC likely has an underlying problem that must be diagnosed by a professional.

Get Support With Your Pressing AC Problems

Is your AC compressor not working? Elkhorn Heating, Air Conditioning, Plumbing & Electrical offers same-day services and upfront pricing throughout the Littleton, Denver, and surrounding metro area.

We will diagnose the cause, explain your AC repair or replacement options, and provide you with transparent, upfront pricing before we begin any work. Call us today at 720-615-0098 or fill out our online form.