How to fix a central air conditioner that won’t start

As summer temperatures soar, a malfunctioning air conditioner can quickly turn a comfortable home into an unbearable sauna. However, with a bit of troubleshooting, you may be able to identify and resolve the issue yourself, potentially saving you the cost of a professional service call. By the end of this guide, you’ll have a better understanding of your air conditioning system and the confidence to handle basic troubleshooting and minor repairs.

If you find out that you need any replacement parts for your appliance while you’re troubleshooting, you can enter your model number at AppliancePartsPros.com to order them. Most orders arrive in just two business days, and we have thousands of free guides to show you how to install your new parts.

The troubleshooting information provided in this article may not apply to your specific appliance model. While we strive to offer helpful advice for DIY appliance repairs, variations in models and configurations can lead to differences in troubleshooting steps, error codes and part replacements. For the most accurate guidance, we strongly recommend consulting the technical sheet for your specific appliance model.

Safety precautions

When working on any appliance, remember to keep safety first. Here are some tips to keep in mind: 

• Always power off and unplug your appliance or switch off the circuit breaker before attempting any maintenance or replacement work. This keeps you safe by preventing any risk of injury from electric shock.
• Wear insulated work gloves to protect your hands from sharp metal parts, pinching hazards and debris.
• Take your time and don’t rush while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access the interior parts.
• Clear your workspace of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with bare wet hands. Make sure the work area is completely dry.
• Check your user manual to see if there are specific installation or safety instructions for your part or appliance. 
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause injury.
• Wear safety glasses when working with chemicals, dust or cleaning large debris to prevent injury. 
• If the appliance has recently been used, give it plenty of time for any heating parts to cool down before working on it. 
• Take pictures or make a note of wiring terminals or other connections before disconnecting to prevent any problems with reassembly.
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.

Tools and materials needed

• Voltage tester 
• Multimeter
• Screwdrivers 

The specific tools required may vary depending on the model of your appliance and the type of fasteners used on it. Always consult the user manual or refer to any specific instructions provided by the manufacturer for the recommended tools for your appliance model.

Troubleshooting steps

Check the power:

1. Ensure the power outlet that the air conditioner is plugged into is functioning properly.
2. Use a voltage tester or lamp to check if there is power at the outlet.
3. If there is no power, check the circuit breaker or fuse that supplies power to the outlet and reset or replace it if necessary.
4. Visually inspect the plug and cord for any damage, such as fraying, cracks, or loose connections.
5. Unplug the air conditioner and check if the plug is properly inserted into the outlet.
6. If the plug is loose or the cord appears damaged, replace the cord.

Check the switch or thermostat:

1. Locate the air conditioner’s control panel or thermostat and ensure the power switch is in the “On” position.
2. If the switch is on, check the thermostat settings to ensure it is calling for cooling.
3. Try adjusting the thermostat to a lower temperature to see if the air conditioner starts.
4. If the switch or thermostat appears to be defective, replace it with a new one.

Inspect the wiring at the control panel:

1. Carefully remove the access panel or cover to the air conditioner’s control panel.
2. Visually inspect the wiring for any signs of damage, such as frayed, broken, or short-circuited wires.
3. If you find any damaged wiring, carefully replace or repair the affected wires.

Test the capacitor and start-relay switch:

1. The air conditioner’s compressor is typically started by a capacitor and a start-relay switch.
2. If these components are faulty, the compressor may not start.
3. You can use a multimeter to test the capacitor and start-relay switch. Replace them if they are found to be defective.

Additional information

Thank you for reading! We hope this guide helped you get your central air conditioner working again.

If you have any other appliance repair needs or projects, don’t hesitate to explore our other troubleshooting guides and videos. 

If you need replacement parts or some extra help with ordering them, grab your model number and head over to AppliancePartsPros.com, where you can chat with a pro, read our DIY blog and more.

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Keep Reading:

How to troubleshoot & fix common window air conditioner problems

How to get better air quality from your window air conditioner 

How to Clean Your Air Conditioner the Easy Way