Solving the Mystery of Your AC Not Working After Power Outages

Woman using a remote control for an air conditioner.

Air conditioners are often left in the lurch following power outages, especially those caused by thunderstorms. Understanding why your AC unit is not turning on after a power outage requires a bit of insight into its mechanics and the impact of sudden power disruptions.

The Impact of Power Surges

A common cause for an AC not working after a thunderstorm is a power surge. When electricity returns post-outage, it can flow back with a higher voltage than your AC unit can handle. This can damage the internal components, leading to issues such as the AC not turning on.

Common AC Power Surge Scenarios

ScenarioDescriptionPotential Impact
Lightning StrikeDirect lightning strikes can cause severe power surges.Extensive internal damage
Grid OverloadWhen power is restored to a grid with a heavy load, surges can occur.Moderate to severe damage
Generator Kick-InPower surges can also happen when backup generators start running.Mild to moderate damage

Circuit Breaker Trips

A tripped circuit breaker is another potential cause of an air conditioner failing to restart after a blackout. In the event of a power loss, voltage variations may cause the breaker to trip.

Common Reasons for Circuit Breaker Trips

Power SurgeSudden voltage spikes can trip the breaker.Prevents electrical damage
OverloadWhen the electrical load exceeds the breaker’s limit.Prevents overheating, fires
Short CircuitA direct path between hot and neutral wires.Prevents electrical hazards

Resetting Post-Outage

Power outages frequently leave air conditioners inoperable, but a simple reset can fix the problem. All you have to do is flip the switch on the thermostat, wait a few minutes, and then turn the unit back on.

Steps to Reset Your AC Unit Post-Outage

Turn Off the ThermostatSet the thermostat to the “off” position.
WaitAllow the AC unit to sit idle for at least 5-10 minutes.
Turn On the ThermostatSet the thermostat to the desired cooling mode and temperature.

DIY Troubleshooting: When Your AC Unit Refuses to Start

If your AC unit is not turning on after a power outage, try these troubleshooting steps before calling a professional:

Check the Thermostat

The thermostat is a critical component of your AC system, as it controls when the unit turns on and off. Follow these steps to ensure the thermostat is not the culprit:

  • Ensure the thermostat is set to ‘cool’ mode. If it’s set to ‘heat’ or ‘off,’ your AC won’t start even if the temperature is too high;
  • Verify that the temperature setting on the thermostat is lower than the current room temperature. If the room is already cooler than the set temperature, the AC may not turn on.

Examination of the Circuit Breaker

Circuit breakers in electrical panels are accountable for supplying power to air conditioning units. It may prevent your air conditioner from commencing if it trips. In order to inspect and recalibrate the circuit breaker, proceed as follows:

  • Identify the Electrical Panel: The electrical panel is commonly situated in the utility room, cellar, or garage of a residence;
  • Identify the AC Circuit Breaker: Locate the breaker designated for your AC unit by opening the electrical panel. It might be labeled “AC,” “Air Conditioner,” or a comparable designation;
  • Reset the Breaker: To reset the circuit breaker, first place it in the “off” position, and if it is currently situated between “off” and “on,” return it to the “on” position;
  • Wait and Listen: Wait a few moments while you listen for the sound of your air conditioner turning on. If it fails to initiate, continue with the subsequent step.

Examine the Outdoor Unit

The outdoor unit of your AC system contains the compressor and condenser coils. It plays a crucial role in cooling the air. Outdoor debris can obstruct airflow and hinder your AC’s performance. Follow these steps to inspect the outdoor unit:

  • Turn off power to the AC unit. You can do this by switching off the circuit breaker or using the disconnect switch located near the outdoor unit;
  • Carefully remove any debris or obstructions around the outdoor unit. Common obstructions include leaves, sticks, grass, and even small animals;
  • Inspect the unit’s fan blades for any damage or blockages. Clear away any debris that may be preventing the fan from spinning freely;
  • After ensuring the outdoor unit is clean and unobstructed, restore power by turning on the circuit breaker or reconnecting the disconnect switch;
  • Wait for a few minutes to see if the AC unit starts running. If it doesn’t, proceed to the next steps.

Persistent Issues: Why Is My AC Unit Not Turning Off?

In the realm of air conditioning systems, encountering a situation where your AC unit refuses to turn off can be quite perplexing. Fortunately, this issue can often be attributed to a handful of common culprits. Let’s delve into the potential reasons behind your AC unit’s persistent operation, how to address them, and preventive measures to keep your cooling system running smoothly.

When confronted with the frustration of an AC unit that won’t shut down, it’s essential to understand the potential underlying causes. Here are some common factors contributing to this issue:

  • Malfunctioning Thermostat: A malfunctioning thermostat is a frequent culprit behind the perpetually running AC unit. If the thermostat fails to accurately sense the indoor temperature or if it’s stuck in the ‘on’ position, it can lead to continuous operation;
  • Frozen Evaporator Coils: Another common issue is the freezing of evaporator coils. When these coils freeze, airflow is restricted, causing the AC unit to work continuously in an attempt to cool the space. This can occur due to inadequate airflow, low refrigerant levels, or other factors;
  • A Stuck Relay: AC units rely on relays to control the compressor and blower motor. If one of these relays gets stuck in the ‘on’ position, it can prevent the unit from turning off as intended.

Now that we’ve identified the potential culprits, let’s explore the steps you can take to address an AC that refuses to power down.

Steps to Address an AC That Won’t Turn Off

Check the Thermostat SettingsExamine the thermostat settings initially. Verify that it is not inadvertently configured to the ‘fan only’ setting, which would cause the extractor fan to operate continuously. Modify the thermostat’s mode and temperature setting to your liking.
Inspect for Ice Build-UpIf your AC unit has frozen evaporator coils, it’s crucial to address this issue promptly. Turn off the AC system and allow it to thaw completely. This can take several hours. Once the ice has melted, check for any signs of water damage or refrigerant leaks.
Seek Professional HelpIf the problem persists despite checking the thermostat and thawing the evaporator coils, it’s advisable to seek assistance from a professional HVAC technician. They have the expertise and diagnostic tools to identify and rectify more complex issues, such as a stuck relay or refrigerant-related problems.

The Aftermath of Thunderstorms: Special Considerations

Thunderstorms can bring their own set of challenges for your AC unit. Electrical surges and physical damage are among the issues that can occur during storms. Here’s what you should do in the aftermath of a thunderstorm:

  • Inspect for Visible Damage: After a thunderstorm, visually inspect your AC unit for any visible damage, such as bent or damaged fins, dented panels, or debris lodged in the unit. Physical damage can impede the unit’s performance;
  • Listen for Unusual Noises: Pay attention to any unusual noises emanating from the AC unit. Strange sounds like grinding, rattling, or hissing may indicate internal damage. If you detect such noises, it’s best to have the unit inspected by a professional.

Preventive Measures: Safeguarding Your AC Unit

To minimize the risk of your AC unit encountering issues, especially after a thunderstorm or power outage, consider implementing these preventive measures:

  • Use Surge Protectors: Protect your air conditioner and other electronic devices with surge suppressors. Protect your air conditioner against the damage that can be done by abrupt voltage spikes caused by storms or power outages with the help of a surge protector;
  • Regular Maintenance: Schedule routine check-ups and maintenance for your AC system. Professional maintenance can identify potential issues before they escalate into major problems. This includes checking refrigerant levels, cleaning coils, and inspecting electrical connections;
  • Inspect Wiring: Periodically inspect all electrical connections and wiring associated with your AC unit. Ensure that they are secure, free from corrosion, and not damaged. Faulty wiring can lead to operational problems and safety hazards.


If your air conditioner won’t turn on after the power goes out, it’s important to know what could be wrong, how to fix it, and when to call a professional. Also, preventative maintenance and checks can help a lot to keep these problems from happening. Remember that if you know what you’re doing and pay attention, you can keep the cool air going even after the storm is over.


Q1. How long should I wait to turn on my AC after a power outage?

A1. Wait at least 5-10 minutes after the power comes back to turn on your AC. This gives the system time to stabilize.

Q2. Can a power surge permanently damage my AC unit?

A2. Yes, a power surge can cause significant damage. It’s advisable to use a surge protector.

Q3. Why does my AC blow warm air after a power outage?

A3. This could be due to a tripped circuit breaker or a reset issue with the thermostat.

Q4. Should I reset my AC after every power outage?

A4. It’s a good practice to reset your AC after an outage to ensure it starts correctly.

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