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With so many different elements to air conditioning systems, keeping track of the current condition of all of them can be a challenge. It is important to know how to recognize when something isn’t right, however, so you can take steps to correct the problem as soon as possible. If your indoor unit turns on and air blows from the vents, but that air is not cold at all, it indicates something else isn’t working correctly. When you check the exterior unit, you might find yourself with the question, “why is my AC outside unit not turning on?”


This can be a confusing situation, especially if the interior unit seems to operate. When the outside part of your system remains silent and still, though, it indicates something is wrong. Let’s explore what this hardware does and consider a few of the things that might be wrong.


What Does the Outside Unit Even Do?


The outdoor unit is where important parts of the refrigeration cycle take place. There is the condenser coil and its fan, which exhausts the heat collected from the air indoors to the exterior. More importantly, there is also the compressor unit, which places the refrigerant gas back under high pressure and sends it back indoors to start the cooling process all over again. Knowing that, let’s look at the key reasons that could be the answer to “why is my AC outside unit not turning on?”


Reason 1: The Circuit Breaker Has Tripped


Sometimes, the problem can be as simple as a tripped circuit or a blown fuse. Check your breaker box in the house and locate the circuit labeled as containing the air conditioning unit. If it has been tripped, reset the breaker and see if the unit turns on now. If it does, you’ve solved your problem. However, you should seek to find out why the unit tripped the breaker in the first place, which may require a professional service visit.


Reason 2: The Unit’s Emergency Shut-Off Tripped


AC units have several kinds of emergency power shut-offs that will trigger to prevent damage to the unit. This shut-off can happen at the outdoor unit itself, such as when it detects some form of electrical fault and powers off. Other times, it can result from a switch tripped indoors, such as when a condensate drain line begins to overflow. You’ll need an HVAC technician to reset the switch and get the unit running again.


Reason 3: Bad Start or Run Capacitors


Inside the outdoor unit, there are several kinds of large power capacitors that store energy and release it to assist the unit at different stages of operation. These “start” and “run” capacitors can go bad over time, and when they do, they can cause your outdoor unit to malfunction. Diagnosing bad capacitors requires a look inside the unit, and only a licensed, trained professional should undertake this take. Never try to examine capacitors on your own — they can hold deadly levels of electric charge that can discharge in an instant.


Reason 4: Insufficient Refrigerant


If your system does not have enough refrigerant pressure in the lines due to a leak somewhere in the system, it may not run correctly at all. You may see the condenser fan spinning, but you may not hear the rest of the unit functioning as it should. Do not run your unit with low refrigerant pressure. Not only will you not cool the home, but you will also waste energy and put unnecessary stress on the unit. Switch it off and call for help, as chemical refrigerants need special handling.


Reason 5: Bad Motors


If you don’t see the fan turning at all, but you can hear the unit trying to operate otherwise, the condenser fan motor may be bad. When that happens, you should also switch off the unit and phone an HVAC technician. The fan is an important part of the unit’s operation, and you could cause damage by operating the unit with a bad motor.


Reason 6: A Blown Compressor


In the worst-case scenario, the compressor itself has stopped functioning altogether. Sometimes called a “blown compressor,” it means your system can no longer achieve the pressure necessary to properly cool your home. This fault usually requires an outdoor unit replacement.


Your Next Steps to Answer “Why Is My Outside AC Unit Not Turning On?”


While there are many possible reasons for a non-functional AC, diagnosing your problem as any one of them can be a challenge without the right tools and training. Know who to call in your area for prompt, reliable service when you notice that things aren’t working as they should. Find professional help when you ask, “why is my AC outside unit not turning on?” and get back to enjoying a comfortable indoor space as soon as possible.