Air Conditioner Troubleshooting: Fixing the Most Common Problems

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Last updated: 
April 29, 2024

Air Conditioner Troubleshooting: A DIY Guide


When your air conditioner fails to work during a heat spell, it can be incredibly frustrating. While most air conditioner repairs should be handled by HVAC technicians, there are some simple repairs you can do yourself with a little troubleshooting. This guide will explore some of the most common problems and how to fix them.

Tools and Materials Needed

Before starting your DIY air conditioner repair project, ensure you have the following tools:

  • Cordless drill or driver
  • Nut driver
  • Adjustable wrench
  • Voltage tester
  • At least 2 insulated screwdrivers
  • Needle-nose pliers
  • Socket set
  • Multimeter

You may also need some materials, depending on the nature of the repair:

  • Fuses
  • Capacitor
  • Contactor
  • Compressed air
  • Condenser fan motor

Common Air Conditioning Problems

1. Your AC Unit Won't Turn On

If your air conditioning system fails to start, there could be several potential causes. First, check if the condenser is running, the thermostat is set properly, and the AC is plugged in. You can try lowering the thermostat by 5-10 degrees to see if the unit will work.

Another potential problem could be a blown fuse. Use a multimeter set to a lower Ohms scale and place the black and red leads on opposite ends of the fuse. A zero, infinity symbol, or minus reading indicates a blown fuse, which could also signify a failure in the condensing unit.

If replacing the fuse doesn't solve the problem, or if the unit won't turn on after replacing the capacitor and contactor, the issue could be with the compressor or motor. At this point, it's best to contact an HVAC professional.

2. Your AC Unit Is Not Cooling Air or Isn't Working Optimally

If your AC system fails to work despite correct thermostat settings, the problem could be a blocked or dirty air condenser. Clean the unit from the outside to remove any weeds or debris blocking the free flow of air.

Also, check the filter for dirt accumulation, which can prevent air from flowing to the evaporator coil. According to our research, filters should be changed at least once a month if you constantly use your AC unit or have pets. If the filter is clean and the AC still fails to work, the problem could be related to the refrigerant or compressor.

3. Leaking Refrigerant

Refrigerant leaks can be a significant issue in air conditioner troubleshooting. If your AC unit is low on refrigerant, it may have been undercharged at installation, or there could be a leak. Refrigerant is the fluid mixture that keeps everything cold, and leaks can be harmful to the environment. To fix refrigerant leaks, you will need a trained technician, as the air conditioner functions optimally when the refrigerant is charged according to manufacturer's specifications.

4. Leaking Ducts

Leaking or dirty ducts can also prevent your AC unit from working efficiently. If you're getting warmer air than expected, there could be a problem with the ducts. Although central air conditioning systems are generally well-sealed, ductwork running through ceilings and walls can develop leaks due to poor workmanship or rodents. When there are leaks in the ducts, cool air escapes before reaching your room. As part of your air conditioner troubleshooting, check the window seals around the AC system to ensure hot air isn't getting in.

Maintenance and Caution

Regular maintenance is crucial for the longevity and efficiency of your AC unit. This includes replacing filters monthly, cleaning the condenser and evaporator coils, and clearing the drain lines at least twice a year.

Before starting any repairs on your air conditioning system, ensure you have turned off the power at both the interior breaker box and the exterior shut-off box near the condenser. If you're unsure about a specific situation, especially those involving electrical components or the core of the system, involve a professional.


The key takeaway from this air conditioner troubleshooting guide is the importance of a routine maintenance plan. Even if the above troubleshooting steps don't work, you'll have covered the most common problems, allowing your HVAC professional to focus on more elusive challenges. By fitting new parts on your AC unit, you can extend its lifespan and reduce the chances of breakdowns. If you have successfully completed a DIY AC repair recently, we'd love to hear about your experience in the comments below.

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