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Why is my AC always breaking?


Seriously?!? Again? Alright, let’s figure out what’s going on and get you cool again. Luckily, Filter King has all the expertise and resources you need to bring your HVAC system back to full health.

Before we begin, Filter King recommends hiring a licensed HVAC professional to work on your system. Doing anything wrong can result in electrocution, house fires, and an explosion. It’s just not worth it.

Now, that doesn’t mean you can’t learn about your system and figure out what’s going on! Let’s get started.

Most Common AC Issues

1.) Incorrect Cooling Unit Size

At a conceptual level, there are only a few causes for an AC malfunction. The first has to do with the capability of your air conditioner. In order to assess this, with need to talk about British Thermal Units.

A British Thermal Unit, or BTU, is a unit of measurement defines as the amount of energy required to heat one pound of water by one degree Fahrenheit. Ok, that’s a little uninspiring for our purposes. So, what is a BTU in the context of air conditioning?

A BTU, in HVAC, refers to how powerful your cooling unit is. The higher your BTU, the more powerful it is, and the more space it can cool down effectively. Many AC problems can come from a BTU that is either too low or too high.

If your BTU is too low, your AC unit will not be able to cool your house down effectively. But gosh dang it, it’s going to try! Think of it like a very short track runner. To cover a mile, he’ll have to be pumping his little legs as fast as he can, with sweat streaming down his face and a ton of chafing (ew.) Conversely, a track runner of average height can cover the same mile with comparative ease.

Air conditioning units that are too weak for your house will keep pumping and pumping as hard as they can all day long until, finally, something gives out.

By contrast, your BTU is also a problem if it’s too high. This can be compared to a freakishly tall track runner. Sure, he can run that mile pretty easily with his long legs bounding dozens of feet at a time. But, if you ask him to keep a certain, slower pace, he’ll have trouble adjusting his speed. If you want him to run a consistent 8-minute mile, but his warm-up mile time is 6:30, he’s going to have stop several times during the mile to maintain that pace.

When your BTU is high, your AC unit can suffer from something called short cycling. This occurs when your AC has cooled down your house to the perfect temperature. The unit’s thermometers will do what they can to maintain that temperature. If your AC unit is too powerful for the size of your house, it won’t be able to give a steady stream of cool air to do this. Instead, it’ll turn on, bring the house back to temperature very quickly, and then turn back off again. And on and on it will go, turning off and on very quickly until something breaks.


An air conditioner that is too powerful can also lead to mold, since it can create condensation on your walls.

Most homes have the correct size air conditioner. This only occurs if the builders of the house did something very wrong, or if the house was made larger or smaller with no change to the AC system. If you suspect this is a problem for your house, check out the graph below and match it with your AC system’s BTU level.


Unfortunately, if this is a problem, you’ll need to replace your entire cooling unit. It’s expensive and can be time consuming, but it’s the only way to fix it permanently.

2.) An Old System

AC systems are designed to last decades. Because they’re so hard to replace, it doesn’t make economic sense to the producers to make one that doesn’t last long – no one would buy it.

Some AC systems from the 1980s are still up and running. This is, of course, the extreme end, and you shouldn’t expect your system to run for 40 years, especially without repairs. That brings us to the next common AC problem.

Every AC system will break down eventually. One of the biggest factors to the longevity of your system is the quality of the repairs that have been made. If your AC system seems to be breaking down often, the cause could be low-quality repairs.

When an AC system breaks down, professionals won’t replace the whole system. That’s like giving your car to the scrapyard just because you got a flat tire. Instead, they’ll just fix the tire.


Many of these small AC repairs are merely band aids to patch up a larger issue. When too any of these band aids are piled on top of each other, the result can be a less reliable AC system that eventually just needs to be replaced.

If your system, is more than a decade old, this is the most likely cause of your regular break downs. To fix it, you’ll need to get a professional to take a look. Depending on what repairs have been made, he may recommend only replacing the cooling unit, the ventilation system, blower, or the electrical system.

3.) Bad Air Filters

The most likely reason your AC is continually going out is a bad air filter. When an air filter gets clogged and backed up with dust and dirt, your AC system can’t get enough air to properly function. It’s like repeatedly trying to breathe through a plastic bag - you’re going to damage your lungs.


Luckily, this is by far the easiest HVAC issue to fix. It’s also the only AC repair you shouldn’t hire a professional for. Your air conditioner’s intakes can probably be opened and closed without tools, and filters are cheap and easy to install.

First, find your intake vents. They’re usually the largest vents in your house, and they’ll have an air filter inside (obviously). Open up the cover (usually a set of hand screws or some tabs) and pull out the filter. You may want to close your eyes when you pull the filter out, because if it’s very dirty, it might send dust into your general eye area. Not fun.

Grab your new filter, make sure it’s oriented for proper air flow (it’ll have arrows on the side, make them point into the vent), and just slide it in. Close the cover, and you’re all set!

Wait, how do I get new filters?

Go take a look at your filter right now. Seriously, go get one of them. We’ll help you out. Got it? Good. Look for the air filter size on the side of the filter (it’ll be in the format NUMBER x NUMBER x NUMBER). Then, go to our online air filter store, select that size, choose what filter quality you want, and your new filters will be there in a few days. It really is that simple.

Be sure to subscribe to your newsletter to learn more about AC systems, home improvement, and air filter troubleshooting in general. If your AC keeps breaking, Filter King’s blog is the best resource you can have on hand.