Your air conditioner should turn on and off two or three times an hour, and stay on for ten to fifteen minutes each time. Short-cycling is when it keeps turning on and off more often, or doesn’t stay on very long. That’s a sign there’s something wrong.
In some cases, you can get to the bottom of a short-cycling problem and fix it yourself. Other times, you’ll need a professional — or even a new system altogether.
In this article, we’ll explain why your AC turns on and off. And, we’ll look at the four most common reasons it’s doing so too often. 
Why Central Air Cycles On and Off
A conventional central air condenser works by cooling your house every time the temperature creeps up higher than you want. When your thermostat reads a few degrees above what you set it for, it turns on your central air. Then, it keeps it running until the house is a few degrees cooler than you want it.
It overshoots so that it doesn’t need to turn on the system again right away. But the point here is that it doesn’t actually maintain the temperature all the time. Instead, it’s always clicking on and off to course-correct.
The notable exceptions here are variable-speed condensers or ones that use inverter technology. You’ll see this in some high-end conventional units and virtually all heat pump mini split systems.
Those ACs run almost constantly. But, most of the time, they are in a quiet, low-power, or low-speed mode that uses very little energy but keeps the temperature even all the time.
At any rate, short-cycling is when the process happens too quickly and too often. You’re less comfortable because it doesn’t cool properly.
And, the system will likely break down from excess wear and tear.
Four Causes When Your AC Keeps Turning On And Off
If your AC keeps turning on and off to often, start by checking for these four common causes:
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Broken Thermostat
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Clogged Air Filter
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Undersized Air Conditioner
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Oversized Air Conditioner
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Broken Thermostat
If your thermostat isn’t working properly, neither will your HVAC system. It may not be measuring the temperature correctly, or it’s sending bad signals.
To check these, grab a thermometer and put it up to the thermostat. Do the readings match? If not, you’ve uncovered a problem.
Next, set the call temperature much higher than you want. Or, much lower. Monitor the temperature on your separate thermometer. See if the system clicks on and off at the right times.
Finally, make sure the thermostat isn’t too close or directly in line with a vent. Sometimes, a blast of cold air directly hitting the gauge causes it to shut the system down quicker because it thinks the room is cooler than it is.
Clogged Air Filter
When’s the last time you changed your air filter? If your answer is more than “three months ago,” then it could be why AC isn’t working correctly.
Really, you should change it once a month. The longer you leave it, the more likely it is to get clogged. And, once enough particles build up, they prevent air from passing through.
This problem can put your system into a loop: Thermostat turns it on because it’s too hot. The system shuts down right away because it recognizes an airflow problem.
But, since it doesn’t cool your home, the thermostat turns it on again — because it’s too hot. Wash, rinse, repeat.
If the filter is grey or darker, it’s clogged. Replace it and start swapping it out way more often.
Undersized Air Conditioner
This is a simple problem with a not-so-simple solution: Your air conditioner is undersized for your home. It’s not strong enough to keep it cool, so it needs to turn on way more often than it should.
You can’t really do much to confirm this on your own. A professional needs to check the system specs and possibly do a load calculation on your house.
That will tell them — and you — if you need a stronger AC.
If this happens, it’s because whatever contractor installed the last one didn’t use one that provided the right amount of strength for your home. And, there’s nothing you can do to make it more powerful.
The best option is replacement — it’ll probably burn out years before it should anyway from being overworked. Otherwise, set the temperature lower, so it doesn’t click on as much, and use fans and dehumidifiers to try an make up the difference.
Oversized Air Conditioner
An oversized AC will cause a lot of the same problems as one that’s too weak: It will turn on and off way too often, it won’t cool your home properly, and it will probably break down in under a decade.
In this case, the problem is too much too fast. You want your air conditioner to work for at least 10 minutes at a stretch. This way, the cool air reaches every corner of your home.
And, it continues dehumidifying. Removing moisture is an essential part of the cooling process. But your AC needs to be running to do it.
A system that’s too powerful won’t do either of these. Instead, it’ll send a blast of cold air into the house, and the thermostat will read this as cool enough.
But, since it shuts off the system too quickly, your home remains humid. And, it never really gets cold enough. So, the condenser clicks back on almost instantly.
Unfortunately, there’s not much we can do besides offering to replace it with a more appropriate model.
Air Conditioner Repairs, Service, and Installation in Havertown, PA
Call or email us at John Cipollone right away if you notice your air conditioner short-cycling, and you can’t get it to stop. You want to nip the problem in the bud before it gets worse. We offer traditional in-person service calls plus virtual meetings and teleconferencing. Either way, we’ll help you get your home comfortable again as soon as possible.