6 Common Reasons Your AC Went Out (and How to Fix It)

Brionna Farney
Written by Brionna Farney
Updated March 9, 2022
A little boy sitting on the floor in front of a big fan
Photo: DimaBerlin / Adobe Stock


  • Ensure your AC has all of the required power sources.

  • Check the batteries in your thermostat.

  • Regularly clean your unit and replace air filters.

  • Keeping up with routine AC maintenance will limit service interruptions.

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Air conditioning units have a peculiar way of breaking down on the hottest days of summer, right when you need them most. Don’t overheat looking for a solution. While your entire AC system may seem complex, the answer to your troubles could be very simple.

Here are some common reasons your AC went out and how to get back to relaxing in that cool, comfortable air.

1. Your Home Lost Power

First and foremost, make sure your home has active electrical power. It may seem obvious, but on a hot summer’s day, you will quickly notice the temperature in your home start to creep up before realizing other electronics are also off. If your home does indeed have power, there are other power sources to check.

Make Sure Your Gas Meter Is On

If your AC unit is gas-powered, the gas meter needs to be turned on. This exterior meter, located near the front of your home, tells your service provider how much gas your system consumes. If you recently moved to a new place, this meter may not be turned on yet and you should call the gas company.

Your Circuit Breaker May Have Tripped

Check your breaker box to see if the breaker for your AC unit has been tripped. You can simply reset the breaker to get your AC working again. Keep in mind, breakers always trip for a reason. If the issue persists, the circuit may be overloaded or there is another issue that should be diagnosed and fixed by a professional HVAC contractor.

2. Your Thermostat Is Broken

Before checking your AC unit itself for any problems, make sure the thermostat is functioning. This handy-dandy device senses the temperature in your home and adjusts the AC accordingly based on your inputs. If your thermostat is not working, your AC will not work. Start by making sure your thermostat is switched on and has not been accidentally turned off.

Make Sure the Batteries Are Not Dead

If the screen on your thermostat is not lighting up, swap out the batteries—easy enough. Note: Smart thermostats do not require batteries, receiving power directly through wiring.

A Fuse in Your Thermostat Could Be Blown

After replacing the batteries, if your thermostat is still malfunctioning, a fuse inside the panel could be blown. Consult an HVAC professional to test your thermostat with a multimeter and make the necessary repair.

3. Your Air Conditioner Is Dirty 

A senior man replacing an air filter
Photo: slobo / iStock / Getty Images Plus / Getty Images

The presence of water, dust, dirt, or grime will cause your AC unit to work inefficiently and potentially stop functioning altogether. Make sure you keep up with regular AC maintenance to avoid any unnecessary service interruptions.

Replace or Clean Your Air Filter

You should be regularly replacing or cleaning your air filter according to manufacturer instructions. If this task is neglected for long enough, the filter will become clogged and restrict the airflow throughout your AC system.

The Unit Coils May Be Dirty

If the air coming out of your AC is not cooled to your liking, the coils might be dirty and unable to efficiently remove heat from your home. Both your indoor and outdoor AC units have coils that require cleaning. A service technician will complete this cleaning task for you if you schedule an annual AC tune-up.

4. The Disconnect Switches Are Off

A disconnect switch, or safety switch, is different from a typical on-off power button. A disconnect switch completely shuts off the electrical circuit to your AC so a technician can safely work on the unit.

You will likely find a disconnect switch on both your indoor and outdoor AC unit. Sometimes this switch can be bumped into and accidentally turned off. Make sure both of your disconnect switches are in the “on” position so electricity can reach and power your cooling unit.

5. A Safety Feature Was Triggered

Your AC unit is smarter than you think. Most systems have built-in safety features that prevent common situations that could lead to damage or harm from occurring. A couple safety mechanisms to check include:

Condensate Overflow Switch  

Your AC unit collects a lot of water, or condensate, from the air it cools and disposes of it through a drain pipe. If the drain pipe becomes clogged, water will build up in a drip pan beneath your unit. To prevent the water from overflowing the pan and potentially damaging your home, the condensate overflow switch will shut off your unit.

Drain Pan Safety Switch

Similarly, this switch aims to prevent water leakage from your AC. If the pan beneath your unit isn’t in the correct position to collect overflowing water, your AC will shut off until the pan is manually adjusted.

6. Electrical Components Are Malfunctioning 

There are hundreds of components that make up the inner workings of your air conditioning unit. With regular use and age, eventually these components will wear down or break and require replacing. If you have already gone through the above scenarios without any luck, there is a good chance your AC went out due to an internal problem.

Electrical issues can vary from blown transformers to faulty capacitors to loose wiring. In any case, if you think your AC unit could have an electrical issue, always consult a qualified electrician or HVAC repair person to diagnose and fix the problem.

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