Air Conditioner Does Not Turn On
If your air conditioner does not turn on, the problem could be caused by a tripped circuit breaker, faulty thermostat, blown fuse, or a failed capacitor. Before replacing any parts, inspect the most common causes listed below.
Safety Notice: Always turn off power to the air conditioner before servicing it. If you notice signs of electrical damage, burning odors, or exposed wiring, disconnect power immediately before inspecting the unit.
Possible Causes
- Tripped circuit breaker
- Faulty thermostat
- Blown fuse
- Failed capacitor
- Defective contactor
- Failed control board
- Loose or damaged wiring
- Failed compressor
1. Tripped Circuit Breaker
Most Common Solution
A tripped circuit breaker prevents power from reaching the air conditioner. This is one of the most common reasons an air conditioner will not start.
What to do:
- Check your home's electrical panel.
- Reset the tripped circuit breaker once.
- If the breaker trips again, discontinue use until the cause has been identified.
2. Thermostat
A thermostat that is incorrectly set or malfunctioning may prevent the air conditioner from receiving a cooling signal.
What to do:
- Verify the thermostat is set to Cool mode.
- Set the temperature below the current room temperature.
- Replace the thermostat batteries if applicable.
- Replace the thermostat if it is defective.
3. Fuse
Some air conditioning systems use fuses to protect electrical components. A blown fuse will prevent the unit from operating.
What to do:
- Disconnect power to the unit.
- Locate and inspect the fuse.
- Test the fuse for continuity.
- Replace the fuse if it has blown.
4. Capacitor
The run or start capacitor provides the electrical boost needed for the compressor and fan motors to start. A failed capacitor can prevent the system from turning on.
What to do:
- Disconnect power.
- Inspect the capacitor for bulging, leaking, or corrosion.
- Test the capacitor using the proper equipment.
- Replace it if it is defective.
5. Contactor
The contactor supplies power to the compressor and condenser fan motor. If it fails, the outdoor unit may not start.
What to do:
- Inspect the contactor for burned or pitted contacts.
- Test for continuity and proper operation.
- Replace the contactor if it is defective.
6. Control Board
The control board coordinates the operation of the air conditioner. If it fails, the system may not respond even when power is available.
What to do:
- Inspect the control board for burned components or visible damage.
- Replace the board if it is defective after ruling out other electrical components.
7. Wiring
Loose, damaged, or disconnected wiring can interrupt power to critical components and prevent the air conditioner from starting.
What to do:
- Turn off power to the unit.
- Inspect accessible wiring harnesses and electrical connections.
- Tighten loose connections.
- Replace damaged wiring as needed.
8. Compressor
A failed compressor can prevent the air conditioner from operating properly and, in some cases, may keep the system from starting.
What to do:
- Listen for humming or clicking from the outdoor unit.
- Inspect the compressor for signs of overheating.
- Replace the compressor if it has failed.
Need Help Finding the Correct Part?
If you need help identifying the correct replacement part, send us your complete air conditioner model number and a clear photo of the appliance identification label before placing your order. Our team will verify compatibility and help ensure you receive the correct replacement part the first time.