How to Repair a Home Air Conditioner

Discover how to troubleshoot and fix home air conditioner problems

HVAC Thermostat

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Project Overview
  • Working Time: 1 hr - 1 hr, 30 mins
  • Total Time: 1 hr, 30 mins - 2 hrs
  • Skill Level: Intermediate
  • Estimated Cost: $10 to $100

A home air conditioning system is an important part of the home infrastructure that helps to keep the home cool during the warmer months of the year so you can escape the heat. When you turn on the thermostat, you expect a rush of cool air from the vents, but if this doesn't happen, your first thought may be to start scanning your phone for HVAC repair companies.

Air conditioner repairs can get costly, so before you look up the company website or make a call, consider taking a couple hours to troubleshoot the issue. In many cases, the problem can be resolved without calling in a professional, saving you money in the process. Use this guide to learn more about potential air conditioner problems and how to complete home AC repair projects.

Common Home Air Conditioner Problems

Condenser Does Not Run

The condenser is the outdoor part of an air conditioning system. If the condenser doesn't turn on, then the air conditioner will not work. This can occur for several different reasons. The most basic issue that could be preventing the condenser from turning on is that the thermostat is currently set too high. If the thermostat temperature is low enough for the condenser to turn on, then the problem could be due to a faulty compressor, faulty motor, or the condenser may not be receiving power. If you suspect that the issue is due to a faulty compressor, faulty motor, or damaged wiring, then it's recommended to contact an air conditioner repair professional.

Uneven Cooling

In some cases the air conditioner could be working properly, but you notice that the home is cooler in some areas than it is in others. This uneven cooling is generally the result of closed or clogged vents. By ensuring the airways throughout the home ventilation system are clean and clear, you should be able to correct the distribution system imbalance.

Inadequate Cooling

If the air conditioner seems to be working properly, but the temperature within the home doesn't drop, despite the air conditioner running constantly, there are a few possibilities that could be the cause. Check to make sure that the thermostat is set to the right temperature. If it is too high, then the air conditioner will automatically turn off before properly cooling the home.

Alternately, the evaporator coils may be too dirty. This can be resolved by cleaning the evaporator coils in most cases. However, another possibility that could lead to inadequate cooling is if the air conditioning unit is too small for the size of the home. In this case, you would need to consult with an air conditioning professional to determine if an upgrade is necessary.

No Cooling

When the air conditioner turns on, but the air coming out of the vents is the same temperature as the rest of the home, it's an indication that the air conditioner is not cooling. If the thermostat is set too high, the air conditioner will not cool the home until it reaches the target temperature. However, if the thermostat is set to a comfortable level, then the issue could be due to dirty condenser coils, dirty evaporator coils, a blocked condensate drain line, low refrigerant levels, or a faulty compressor.

Experienced DIYers can typically handle cleaning condenser and evaporator coils, and may be able to clear a blocked condensate drain line, but it's recommended to contact an air conditioner repair professional to replace a faulty compressor or recharge refrigerant levels.

Condenser Turns On and Off Repeatedly

The air conditioner may attempt to turn on when the temperature inside the home reaches the set level on the thermostat, but if the condenser is blocked by trees, flowers, bushes, or any other obstructions this could cause the condenser to turn on and turn off repeatedly. The issue could also be the result of faulty wiring, dirty condenser coils, or dirty evaporator coils.

Cutting back the foliage around the unit may be all that's required to solve the problem, but you might need to clean the condenser or evaporator coils to resolve the issue. If you suspect the wiring is damaged, causing intermittent power problems with the unit, then contact an air conditioner repair professional to repair or replace the wiring.

Faulty Thermostat

If the thermostat isn't working right, nothing else with the HVAC system will work right. The thermostat is the brain of the entire system. All thermostats need power. Thermostats can be powered by batteries, by a low voltage wire, or by both. If power is compromised, the thermostat will not work. Additionally, thermostats aren't always well-placed in the home. Yours may have been installed where sunlight hits it or next to a cool area with a draft.

What You'll Need

Equipment / Tools

  • Flashlight
  • Screwdriver
  • Shop vacuum
  • Shovel
  • Pruning shears
  • Hand mirror
  • Stiff-bristle brush


  • Replacement fuse
  • Thermostat battery
  • Replacement air filter
  • Microfiber cloth
  • Duct tape
  • Coolant line insulation


How to Repair a Home Air Conditioner

  1. Check the Breaker or Fuse Panel

    A common issue that can occur with the home air conditioning system is that a power surge or short could cause the breaker to trip or a fuse to blow. If the air conditioner doesn't seem to have power, check the breaker panel or fuse panel. Flipping a breaker back into position or replacing a blown fuse should resolve the issue, but if the same problem happens again, you may have a more serious electrical problems that should be handled by an air conditioner repair professional or an electrician.

  2. Change the Filter

    When set at the correct temperature, the air conditioner should blow cold air, not warm or hot air. If this occurs, the system may have a dirty air filter. Replacing the air filter on an HVAC system is relatively easy and should be included as a part of your regular maintenance schedule. Remove and replace the clogged filter with a new filter, making sure that the new filter is installed in the correct direction as indicated by the arrows on the body of the filter.

  3. Test the Thermostat

    Another common cause of problems for your air conditioner is the thermostat. This piece of the system is essentially the brains of the air conditioner, where you can set the exact temperature at which you want the air conditioner to activate. However, if the batteries in the thermostat are dead or the low voltage wire connection is loose, then the thermostat cannot send a signal to the air conditioner to tell it to turn on. Replace the battery or check the low voltage wire connection to restore power to the thermostat.

    If the thermostat has power, then the issue may be because the temperature is set too high. Lowering the temperature should activate the air conditioner. Though, in some cases the thermostat is placed in direct sunlight or positioned in an area that is prone to cool drafts. If this occurs, the temperature reading on the thermostat may not accurately gauge the temperature throughout the home. Consider moving the thermostat yourself if it is a battery-powered device or have an air conditioning professional relocate the thermostat to a more suitable location if it is hardwired to the HVAC system.

  4. Remove Ice Build-Up

    In some circumstances the air conditioner may operate for an extended period of time in an attempt to lower the temperature within the home. During this time, ice can build up on the air conditioner. The fix for this is easier than most. Either turn the cooling system off, so that only the fan operates, or simply turn off the HVAC system. This will allow the ice to melt on its own, freeing the air conditioner.

  5. Clean the Vents

    Cooled air needs to be forced through the ventilation system so that it can reach the furthest areas of the home, but if the vents are closed, blocked, or partially blocked, then it can lead to inadequate or uneven cooling. Check the vents throughout the home to make sure that they are open, clean, and that nothing is sitting on top of or in front of the vents, like an area rug or furniture.

  6. Clear Space Around the Compressor

    Depending on your HVAC setup, the compressor could be positioned at the front, side, or back of the home. In most cases, there is a substantial amount of space around the compressor to allow for unimpeded air flow. However, if the compressor is located in a garden, under trees, or close to the bushes, then extensive growth during the warmer months of the year can obstruct the function of the air conditioner.

    Trimming down any bushes, trees, and other foliage should prevent the compressor from overheating or becoming obstructed. Make sure there is about two to three feet of space around the unit and about five feet of clearance above the unit.

  7. Inspect the Air Ducts

    Ensuring the vents are open, clean, and clear of obstructions is necessary for even, efficient cooling throughout the home. However, even with clean vents the airflow can be restricted if the ducts are too dirty. Inspect the air ducts for signs of significant dust, hair, dirt, and debris build-up. You can typically vacuum a short stretch of air ducts, but for longer runs it's recommended to call an HVAC maintenance professional to clean the ducts throughout the entire home.

  8. Clean the Evaporator Coils

    When the evaporator coils are dirty, it can reduce the cooling output of the air conditioner. If the issue is not resolved, you may notice that the air conditioner is not cooling or it is cooling inadequately to lower the temperature in the home. In some cases, a dirty evaporator coil could also cause the air conditioner to turn on and off repeatedly.

    Check your HVAC system to determine if the evaporator coils are accessible. If the evaporator is accessible, it will be located behind foil-wrapped insulation at the front of the plenum box. Turn off the air conditioner, then remove the tape and the screws holding the access plate in position.

    Use a stiff-bristle brush and a mild detergent to clean the entire evaporator unit. You can use a small hand mirror to help see what you are doing. Also, make sure to clean the collection tray below the evaporator unit, then use a wet/dry shop vac to clean out the drain line. Reinstall the access plate and tape the insulation back into position.

  9. Clean the Compressor Coils

    Dirty compressor coils can cause just as many issues as dirty evaporator coils. Head outside to the compressor and inspect the coils for dirt, dust, and debris. Use a mild detergent and a soft-bristle brush or microfiber cloth to clean the coils. After cleaning the coils, take a few minutes to disconnect the condensate drain line and use the shop vac to suck out any obstructions.

  10. Examine the Coolant Lines

    Most air conditioning system use a refrigerant known as Freon as a coolant. If the coolant lines are damaged, then there could be a leak in the system. When the coolant levels are too low, the air conditioner will not be able to properly cool the home.

    Replace any damaged or worn insulation on the coolant lines and check for leaks. If you spot any leaks or notice the coolant levels are too low, contact an air conditioner repair professional. Do not attempt to patch the leak or charge the system's coolant lines.