Picture this: you’re enjoying your air conditioner on a sweltering summer day when it suddenly powers off. You have no idea why… it’s still quite warm in your home. And to make matters worse, it won’t turn back on. Has your system given out completely? Is it time to replace it outright? Have you experienced a serious issue that’s going to require an extensive and extremely costly repair? Believe it or not, there’s a good chance your issue might be smaller and simpler than you thought. This blog will take a look at three of the reasons that your air conditioner may have shut off unexpectedly and help you potentially solve this problem for yourself.

Your Thermostat Battery Has Quit

This most common reason your air conditioner may have shut off on you is also perhaps the silliest. However, we get a lot of calls every year from customers concerned that their air conditioner has quit on them, but whose actual problem maybe something as small as a battery. Your thermostat does not run on raw AC power alone—it needs a battery to operate. If these batteries die, so does your thermostat. And most air conditioning systems have a safety installed that kills the system should it lose its connection to the thermostat. The easiest way to tell that this is your problem is that your thermostat has shut off and gone completely non-responsive.

Thermostats usually run on a 9V battery, one of those small block-shaped ones. However, modern thermostats have also begun to utilize AA and AAA cells due to their commonality and low cost. Simply remove the thermostat unit from your wall and you should either locate the battery or a battery cover door on the backside of the thermostat. Simply remove that cover to expose the battery, swap it out for a new one (or set of new ones) and you should see the screen on your thermostat come back to life. Then simply replug and replace the thermostat and your air conditioner should turn on again.

Your Air Conditioner Is Frozen

It surprises a lot of people to learn that a frozen air conditioner is actually not only possible on a sweltering summer day, but that it’s actually more common during these hottest summer days than it is on a cooler day. Essentially, a frozen air conditioner’s cause can be boiled down to a combination of a few different factors: insufficient airflow over your evaporator coil and an excess of water in your air conditioner’s air handler.

As air passes over your evaporator coil, the freezing-cold refrigerant in the lines quickly cools the air. As it does this, the freezing-cold surface of the coil also condenses water vapor out of the air, turning it to a liquid form that drips off of the coil and drains away through your condensate drain. However, should there not be enough heat in the air that travels over this coil, the refrigerant’s temperature can’t rise up high enough to continue to flow normally. As such, it continues to get colder and colder until it quite literally begins to freeze water vapor from a gas to a solid state almost instantly. When this happens, the frozen vapor begins to freeze more vapor, and the block of ice on your coil grows and grows until airflow is blocked completely.

Most air conditioner units have a sensor to detect when the system freezes, and they’ll shut off automatically as a safety feature to protect the system and prevent a potentially catastrophic failure. If your system has shut down, this could be the reason why. Allowing your coil to defrost and the water to drain away through the condensate drain will fix the issue. Likewise, changing your air filter will increase airflow through your air handler, ensuring that your air conditioner runs more efficiently, and that your coil receives the amount of air it is designed for, thus preventing the freezing.

Your Circuit Breaker Has Blown

Because your air conditioner uses such a huge amount of electricity, most electrical grids are designed to keep the air conditioner on its own independent circuit. This helps prevent an electrical surge from overdrawing one particular circuit, and prevents damage to anything else that may be plugged into that same circuit should anything go wrong. However, as circuit breakers age, they become less reliable, and running your system for hours on a hot day also contributes to wear and tear on a breaker. When the breaker wears out, it will start to trip more frequently, and it will do this far easier during the extreme conditions of a sweltering summer afternoon.

If your air conditioner gives out and refuses to turn on again, check your circuit breaker. If the breaker is shut off, reset it and your air conditioner should roar back to life. If it does, then the good news is you found the issue. However, you should still have a professional electrician come out and check the circuit to see if there is anything wrong with it. You may want to replace the breaker if it is worn out.

Has your air conditioner quit on you unexpectedly? Call All Pro Plumbing, Heating, Air & Electrical at (909) 500-8193 and let our experienced, highly-trained technicians help you get to the bottom of it!