AC Not Turning On After Power Outage

On this page

Quick answer
Confirm the symptom
Tools and prep
Step-by-step troubleshooting
Common causes table
Parts matching
When to call a pro
FAQ
Related guides

Quick answer

After a power outage, check your thermostat settings and circuit breaker. If the AC still doesn't turn on, wait 30 minutes for the pressure to reset, then try again. If it fails, inspect the capacitor or contact a professional.

Confirm the symptom

AC did not turn on after power was restored
Power is back to the house but AC remains off
Thermostat has power but AC doesn't respond

Tools and prep

Non-contact voltage tester
Screwdriver set
Flashlight
Thermal imaging camera (optional)
Turn off power at the circuit breaker before inspecting the unit

Step-by-step troubleshooting

Check Thermostat Settings
Do: Verify the thermostat is set to 'Cool' and the temperature is lower than the room temperature.
Observe: Thermostat settings are correct.
Means: The thermostat is functioning properly.
Next: Check circuit breaker
Check Circuit Breaker
Do: Locate the circuit breaker panel and ensure the AC's breaker is in the 'On' position.
Observe: Breaker is tripped or damaged.
Means: A tripped breaker may have caused the AC to shut down.
Next: Reset the breaker and wait 5 minutes
Reset the Breaker
Do: Turn the AC's breaker off and then back on.
Observe: Breaker stays in 'On' position without tripping.
Means: The electrical issue may be resolved.
Next: Wait 5 minutes and try turning on the AC
Wait for Pressure Reset
Do: Allow the AC system to rest for 30 minutes to reset refrigerant pressure.
Observe: AC starts after the waiting period.
Means: The system needed time to reset after the outage.
Next: Monitor the AC for normal operation
Inspect the Capacitor
Do: Turn off the power and check the capacitor for bulging, leaking, or burning.
Observe: Capacitor shows signs of damage.
Means: A faulty capacitor may prevent the AC from starting.
Next: Replace the capacitor if damaged
Check the Contactor
Do: Inspect the contactor for signs of wear or damage.
Observe: Contactor is pitted or not closing properly.
Means: A faulty contactor may prevent the AC from receiving power.
Next: Replace the contactor if damaged
Test the Start Relay
Do: Use a multimeter to test the start relay for continuity.
Observe: Relay has no continuity or shows resistance outside the normal range.
Means: A faulty relay may prevent the compressor from starting.
Next: Replace the start relay if faulty
Check for Error Codes
Do: Look for error codes on the thermostat or control panel.
Observe: Error code is displayed.
Means: The error code indicates a specific issue with the system.
Next: Refer to the manufacturer's manual for the error code explanation

Common causes

Cause	Likelihood	Difficulty	Part often needed
Tripped Circuit Breaker The AC may have drawn too much power during startup after the outage.	Common	Easy	None
Faulty Capacitor A damaged capacitor can prevent the AC from starting after a power interruption.	Common	Easy–Medium	Capacitor
Low Refrigerant Low refrigerant levels can cause the system to shut down during or after an outage.	Sometimes	Hard	Refrigerant
Failed Contactor A worn-out contactor may not close properly, preventing the AC from receiving power.	Sometimes	Medium	Contactor
Thermostat Malfunction The thermostat may not be sending the correct signal to the AC unit.	Sometimes	Easy	Thermostat
Start Relay Failure A faulty start relay can prevent the compressor from starting.	Rare	Medium	Start Relay
Frozen Evaporator Coil A frozen coil can cause the system to shut down and not restart after an outage.	Rare	Hard	Defrosting Equipment

Parts matching

Common parts that may need replacement if your AC doesn't turn on after a power outage include:

Capacitor – if it's swollen, leaking, or burned
Contactor – if it's pitted or not closing properly
Thermostat – if it's not responding or sending signals
Start Relay – if it's not providing power to the compressor
Refrigerant – if the system is low on refrigerant and the pressure is too low

Always turn off the power at the circuit breaker before inspecting or replacing any parts to ensure safety.

When to call a professional

The AC still doesn't turn on after following all troubleshooting steps
You notice a burning smell or unusual noises coming from the unit
The capacitor or other electrical components are visibly damaged
The system displays an error code you can't identify or resolve
You're unsure about any step in the troubleshooting process
The AC starts but doesn't cool properly after the outage

FAQ

Why won't my AC turn on after a power outage?

Your AC may not turn on after a power outage due to a tripped circuit breaker, a faulty capacitor, or a refrigerant issue. Follow the troubleshooting steps to identify and resolve the problem.

How long should I wait for the AC to reset after a power outage?

Allow the AC system to rest for at least 30 minutes after a power outage to reset the refrigerant pressure before attempting to turn it on again.

Can a power outage damage my AC system?

A power outage can potentially damage your AC system, especially if there's a power surge when the electricity is restored. Using a surge protector can help prevent such damage.

What should I do if my AC starts but doesn't cool properly after an outage?

If your AC starts but doesn't cool properly after an outage, check for error codes, ensure the thermostat is set correctly, and inspect the air filter. If the issue persists, contact a professional HVAC technician.

Is it safe to reset the circuit breaker for my AC after a power outage?

Yes, it's safe to reset the circuit breaker for your AC after a power outage as long as you follow proper safety precautions, such as turning off the power at the circuit breaker before inspecting the unit.