Why Is My Outside AC Unit Not Running But Inside Is?

air conditioner condenser unit depicting outdoor ac unit not working but inside is

Winter has faded and temperatures are rising. In some places, it is hot enough to merit assistance from an air conditioner. Perhaps you’ve tried to turn on your AC only to find out that it isn’t working right. For example, maybe the outside AC unit not running but inside is. It is a common HVAC issue with several possible causes. Read on to learn more about what you can do.

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Why Is My Outside AC Unit Not Running But Inside Is?

In cooling systems, the indoor and outdoor HVAC units work in tandem to produce the desired results. If one of these is not working, then the house will not cool down no matter how long you wait. There are two ways to determine whether the outside air conditioning unit is not running:

1. No Sound Coming From The Condenser

air conditioner condenser fan close up

One is the complete absence of sound. Some units are built to operate quietly but they should still produce a low hum. If you can’t hear anything, then that means the motors and compressors are not working as they should.

2. Warm Air From The Indoor Air Handler

Put a hand against the AC’s indoor unit and/or your HVAC air vents. If you feel hot air blowing in instead of cold air, then the outdoor unit is not doing its job correctly. The warm summer air is simply passing through the system instead of being cooled by the equipment.

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What Causes The Outdoor Air Conditioner Fan To Stop Working?

You can often isolate the problem to a fan failure. The blades are not moving but the other parts of the outdoor unit may be fine. This can happen even if you are diligent about changing the air filters and other maintenance tasks. Below are the most common reasons why the fan stops spinning:

1. Deficient Power Supply To The Air Conditioner

image of an air conditioner compressor repair

Fan motors run on electricity. If they are not getting enough power, then they will not be able to spin properly. It can be difficult to determine what the exact inhibitor is in various cases. An experienced HVAC technician should come to make an accurate diagnosis.

2. Contactor Problems

The contactor is responsible for controlling the fan motor. Any sort of failure for this component can stop the blades from spinning. It is not advisable to try to fix this yourself since it might end up in a worse state in the hands of a novice. Go straight to an expert right away for a reliable solution.

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3. Burnt Out Fan Motor

Motors can burn out when subjected to excessive stress. They also succumb to wear and tear over time, with poorly maintained systems experiencing this faster than usual. Regular tune-ups are essential in fixing problems at the earliest stages and avoiding expensive repairs in the future.

4. Bad Capacitors

multimeter and run capacitors of an outdoor air conditioning unit

Outside fan failures can also be attributed to bad capacitors. These components store energy to keep the blades spinning. You can compare them to batteries that lose their ability to store energy after heavy use. They can also be damaged by high temperatures and power surges. If a capacitor fails, then it won’t be able to power the fan.

To check whether this is the problem or not, you can slide a long wooden stick through the fan grate. Use this to rotate the blades with a gentle nudge. If these blades start spinning, then you are probably dealing with a bad capacitor. After a while, the fan won’t run even if you kickstart the process. Replacement should be left to the professionals since high voltage and sensitive electrical components are involved.

5. Debris On The Axle

Your external force, as applied through the stick, should be enough to make the blades spin. If you are having trouble with this, then check the fan axle for debris. Dirt may have also accumulated in the motor’s bearings. Get a technician to disassemble and clean all components for unimpeded movement.

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What If The Entire Outside Air Conditioning Unit Isn’t Functioning?

In some cases, it’s not just the fans that have completely stopped working. The whole outside unit isn’t working at all. This is a major headache for homeowners that may require professional help. No one wants to deal with a non-functioning AC in the middle of summer, so act quickly to get it fixed. Let’s go through the possible causes for this sudden system breakdown.

1. Thermostat Settings

image of homeowner adjusting programmable thermostat

Before exploring the worst-case scenarios, check the basics to make sure that the system is set up correctly. Begin with the thermostat settings. Someone could have pushed the wrong buttons and set the temperature too warm. Try a lower temperature setting and see if that makes a difference. You might even discover that it isn’t powered on. Replace the batteries to get it going again.

2. Dirty Outside Compressor Unit

Compressors can overheat if the outdoor unit gets too dirty. A thick layer of dust may prevent heat from escaping to the outside air. If the system is no longer able to tolerate the situation, then it will simply shut down. Inspect the unit to see whether dirt and debris have gotten out of hand. Turn the power off and disconnect the unit before cleaning. Better yet, call an experienced HVAC contractor to do this for you.

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3. Safety Switch Lock

Cooling systems have safety switches that lock the outdoor unit when they sense danger. Performing a reset will get them going again. You can do this by turning the system off from the thermostat or the breaker. After waiting for a minute or so, turn it on again and see if it’s back to normal. If not, then you will need to hire a professional for further troubleshooting.

4. Tripped Circuit Breaker

circuit breaker box

If there was a recent thunderstorm, then your circuit breakers may have gotten overloaded due to power surges. You can check your circuit panel to see if any of the breakers were tripped. Turn them off before turning them on. For older homes, you may have a fuse box with blown fuses. Replace these fuses. If your AC has a fuse at the shut-off box, then call a technician to replace it for you. Sometimes breakers trip repeatedly despite attempts to normalize the situation. This points to a deeper electrical problem that only a licensed electrician can resolve.

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5. Compressor Failure

The compressor is the most important component of the entire AC. It is responsible for pumping the refrigerant across the system at just the right pressure level. If it fails, then the air conditioner will lose its ability to cool indoor air. You will know that it is failing when it stutters or produces a loud noise when you turn it on. Eventually, it will refuse to turn on at all. Fixing this will cost a lot of money. You might even have to upgrade the whole system.


It can be confusing to see that the outdoor unit is not running when the indoor unit is working fine. A quick investigation may reveal the likely culprit, and sometimes things can return to normal with minimal effort. However, it is also possible that the problem is more complex than any regular person can handle. Call professional HVAC technicians as soon as you can and tell them about the situation. They will figure out the root cause and perform the necessary repairs. Once they are finished, the air conditioner will run smoothly once again. Also, be sure to schedule central air conditioner maintenance on an annual basis. This helps prevents problems from escalating while ensuring your comfort and efficiency.

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McAllister EnergyMcAllister Energy offers superior heating and cooling services in Camden County, New Jersey. We hire the best-certified technicians who can provide you with excellent HVAC tune-ups, repairs, installations, and replacements. Each of our techs has the knowledge and experience to service your HVAC system correctly.

McAllister Energy guarantees the most competitive heating and cooling service costs in the area. Our maintenance services can improve your comfort, increase your energy efficiency while reducing your home heating and cooling costs. If you happen to need an HVAC repair or replacement system, we can recommend the best one for your home while staying within your budget. We back all of our work with a guarantee to ensure your satisfaction. To schedule a service appointment, give McAllister Energy a call today. We offer free, in-home estimates.

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