AC Won't Turn On: Helpful Troubleshooting Steps

On a warm day, there’s nothing more frustrating than an AC that won’t turn on. It can quickly send homeowners spiraling about expensive repairs or, worse, a complete replacement. If your air conditioning is struggling to work as it should, this article will provide some troubleshooting tips that may help it work properly again. If these methods don’t work, it may be time to call in an HVAC professional. First, let’s try to identify and fix your current AC problem.

How Air Conditioners Work

AC units typically have three main parts: the compressor, the condenser, and the evaporator. The first two are typically located outside the home, while the evaporator is often found inside where the AC handler is located.

The process starts when cooling fluid enters the compressor as a low-pressure gas. The compressor squeezes the fluid and the molecules become tightly packed. The more the molecules are forced together, the higher the temperature and energy produced. The fluid exits the compressor as a high-pressure gas before moving to the AC condenser. This works like a radiator, helping heat dissipate quickly.

The fluid that leaves the condenser is much cooler and has changed from gas to liquid as a result of the high pressure. The fluid then goes into the evaporator, where the pressure drops. The fluid then begins to evaporate as a gas.

As this happens, the heat is extracted from the surrounding air. Heat is necessary to separate the molecules of the liquid into gas. The metal fans on the evaporator exchange thermal energy with the surrounding air. When the refrigerant leaves the evaporator, it is in the form of a low-pressure, chilled gas. The process begins all over again as it goes through the compressor. A fan inside the unit circulates the air around your property. As you can see, with so many components to consider when your AC is not working, it makes taking a DIY approach to repairs much more difficult, which is why calling a local HVAC professional to diagnose and fix the problem is usually the best, most reliable option.

However, there are some instances when identifying why your AC is not working is just a matter of checking a few less complicated components with a relatively easy fix. Let’s review some common reasons why your AC may not be working and what you can do to fix the problem.

Common Reasons Why Your Air Conditioner is Not Turning On

Thermostat issues are often to blame when an air conditioner is not turning on. Think of your thermostat as your method of communicating with your AC. If it’s not working properly, there’s no way for your system to know it should be switched on. Resetting your thermostat is often all that’s necessary to get it working again.

A tripped circuit breaker is another common reason why your AC won’t turn on. Using too many appliances at once can trip the circuit breaker. This is also common when there are power surges after a big storm. To reset it, find your electrical panel (usually located in your garage) and check to see if any of the breakers have been tripped. Flip the breaker from on to off and back again. Then check to see if this fixed the issue.

Another possible reason your AC is not working is that your condenser unit has come unplugged. This is especially common with window units. Be on the lookout for a brown cord coming from your unit that is connected back to a panel on the side of your home. These wires may become unplugged or even chewed by an animal. This will stop the flow of electricity to your unit, which will prevent it from starting up.

Troubleshooting a Broken Air Conditioner

Troubleshooting an AC unit that’s not turning on can help you diagnose the issue yourself. If these tips fail to resolve the issue, it’s time to call for professional support.

• Check Your Thermostat. Make sure your thermostat is set to COOL, and the temperature is set at least 5 degrees below the current indoor temperature. A family member may have changed the settings, or the thermostat may have accidentally been switched to ‘off’.
• Check Your Air Filter. The air filter is another common reason why your AC won’t turn on. Filters need regular cleaning and replacement. If it’s been a while since your filter was replaced, the odds are good that it’s covered in dust. Dusty filters can clog your system, forcing the AC to work extra hard to reach your desired temperature. This often triggers the system’s self-preservation mode and turns it off entirely. Try swapping your filter for a fresh one every three months to prevent this issue.
• See if the Emergency Shut-Off Switch Is OFF. This is usually located next to the outside AC unit in a metal box hanging on your house. If someone has recently worked on the AC unit, they may have accidentally left this switch in the OFF position.
• Check the Inside Unit’s Power Switch. Sometimes a switch in the air handler closet/crawl space/attic that looks like a light switch controls power to your HVAC; make sure this wasn’t accidentally flipped to the ‘off’ position.
• Make Sure the Drain Pan & Lines Aren’t Clogged. When your AC system runs, it creates condensation that exits your home via a drain line. If the drain pan is full and/or clogged, it will trigger a safety switch, turning off your system. The drain line can be unclogged with a wet/dry vac or pipe snake. Clearing the drain line blockage could easily solve the problem.
• Look for a RESET Button. Some systems have a RESET switch on the outside unit. You can push this and see if it helps. If your unit does not, you can turn off the system at the thermostat, wait 5 minutes, and try again. Note that this is only a temporary solution since a professional will have to inspect the unit to identify why it is shutting off.
• Look for Icy Buildup. If you see any icy buildup on system components, let it thaw before you try to turn the unit on again. The bad news: This can take up to 24 hours. If the coil is clogged by dirt, blocking airflow, it will cause the temperature to drop and freeze up, preventing your system from running. Low refrigerant and improper fan operation can also cause this issue. In any case, if you see this is the issue, you need to call a pro to fix it.

AC Unit Still Not Working?

Although some AC issues are easy to resolve, most require the experience and expertise of a pro. If you’ve followed the tips mentioned above and your AC won’t turn on, it’s time to have a professional assess the situation. Your local Aire Serv^® team can take a thorough look at your system, including other components like, your thermostat, filters, and vents, and provide guidance on possible repairs or replacements. We can also test your indoor air quality and make recommendations on ways to improve it. To learn more, call us or schedule an appointment online today.