How to Do Basic Window Air Conditioner Repairs

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Project Overview
  • Working Time: 30 mins - 3 hrs
  • Total Time: 1 - 4 hrs
  • Skill Level: Intermediate
  • Estimated Cost: $0 to $200

In the midst of summer’s scorching heat, your window air conditioner might be the only thing keeping the blistering outside temperatures at bay. As great as they are, window air conditioners are susceptible to a variety of mechanical and electrical defects, and hiring a professional service technician can be expensive. Fortunately, you can troubleshoot and fix five common issues yourself with minimal time, effort, and materials. Read on to discover how it's done, and learn what preventive maintenance steps you can take to avoid future problems.

Before You Begin

Before you begin troubleshooting, it’s helpful to familiarize yourself with the individual components of your air conditioner. This will help you see what role each one plays in keeping your space cool, and help you determine which one is malfunctioning. 

  • Face panel: Also known as the grille cover, this is the plastic or metal cover attached to the front of your air conditioner. The face panel is the first thing that needs to be removed to access the rest of the air conditioner's parts. Depending on the unit, the face panel may be held in place by screws, tabs and clips, or both.
  • Filter: A thin, pleated screen that protects the air conditioner’s internal components from the damaging effects of dirt and debris and cleans the air before it's recirculated back into the room. The filter will either be located inside or directly behind the face panel.
  • Evaporator: Located directly behind the filter, the evaporator is composed of copper tubing (evaporator coil) surrounded by thin aluminum fins. The evaporator coil contains refrigerant to convert your room's hot air into cold air. 
  • Condenser: Located on the very back of the unit, the condenser has the same components as the evaporator (copper tubing, fins, and refrigerant), but it captures the room's hot air and releases it outdoors with a fan (the condenser fan). 
  • Refrigerant: A liquid (in the condenser) or gaseous (in the evaporator) compound that circulates through the air conditioner’s evaporator and condenser coils to capture and/or cool hot air.
  • Compressor: Compresses the refrigerant into a hot liquid for the condenser and a cold liquid for the evaporator. The compressor is typically located between the evaporator and condenser and is operated by an internal motor (compressor motor).
  • Capacitor: A cylindrical device that stores an electrical charge to start and operate the compressor and fan motor. The capacitor usually connects to the compressor and fan motor with two electrical terminals that protrude from the top of the cylinder.
  • Compressor fan: Blows outside air against the compressor coils to cool them.
  • Blower: Located on the other side of the fan, the blower pulls the room's hot air over the evaporator coils to cool it down before recirculating it back into the room.
  • Thermostat: Responsible for sensing the room's temperature to regulate the air conditioner's on/off cycle. The thermostat is often a small copper tube about three or four inches long, and usually clipped onto the front of the evaporator.
  • Drain pan: The pan on the bottom of the unit that collects the moisture produced from the evaporator. The drain pan is tilted at an angle towards the back of the unit to direct the moisture into the drain port, and to prevent moisture from leaking into your room.
  • Drain port: A small hole in the back of the drain pan. It's connected to a small plastic drain tube that directs the moisture outside your home.

Safety Considerations

To prevent the risk of electrocution, ensure that your air conditioner is disconnected from electricity. This can be done by unplugging the power cord from the wall, or shutting off the circuit breaker that operates the air conditioner on your home’s main electrical panel.

  • Even with the unit turned off, the capacitor may still be storing a large amount of electrical energy. Before you attempt any repairs on the capacitor, condenser, or fan, it’s important to properly “discharge” it to release its stored electrical energy. Ensuring that you’re only holding the screwdriver’s insulated handle, and not touching any metal portion of the screwdriver, touch the metal end of the screwdriver across the capacitor’s two terminals simultaneously. When successfully performed, you should hear a popping noise and/or see a spark.

Warning

The capacitor can store a large electrical charge, and you should hire a processional air conditioner technician if you're uncomfortable performing this step.

What You'll Need

Equipment / Tools

  • Shop vacuum
  • Cloth or rag
  • Small knife with thin blade, or an AC fin comb
  • Screwdriver with insulated handle
  • Digital multimeter
  • Bubble level
  • Non-contact voltage tester (optional)

Materials

  • Air conditioner coil cleaner
  • Can of compressed air
  • PVC cleaning solution or white vinegar

Instructions

Air Conditioner Not Cooling

An air conditioner that isn’t cooling can be caused by:

  • A dirty air filter
  • A dirty condenser
  • A dirty evaporator
  • Bent condenser or evaporator fins
  • Low or leaking refrigerant
  • A bad capacitor
  • A bad compressor motor

How to Repair an Air Conditioner That's Not Cooling

  1. Clean the Filter

    Remove the filter from the face panel using the instructions supplied in your air conditioner's user's manual. For a lighter clean, you can vacuum dirt and debris off the filter with a vacuum, or wipe the filter down with a wet rag. For a deeper clean, you can take the filter outside and spray it off with a garden hose. In either case, allow the filter to completely dry (30 minutes to an hour) before reinstalling it.

  2. Clean the Evaporator and the Condenser

    Clean the evaporator and condenser with a vacuum. For a deeper clean, spray them off with compressed air, or spray them with an air conditioner coil cleaner. 

  3. Fix the Fins

    Straighten any bent evaporator or condenser fins with a knife or fin comb.

  4. Check the Refrigerant Lines

    Inspect your refrigerant lines for evidence of low or leaking fluid. Symptoms of low refrigerant can include ice formation on the evaporator coils and hot air being emitted from the unit. Bubble formation or hissing and gurgling noises can indicate a leak in the refrigerant lines. If any of these signs are present, contact a qualified AC service technician to refill, repair, or replace the refrigerant lines. 

  5. Check the Capacitor

    Visually inspect the capacitor for any bulging, deformations, or leaking fluid. If no visual symptoms are present, test for an electrical defect with a digital multimeter. The capacitor’s “capacitor rating” will be marked on the cylinder, and should be listed in your air conditioner’s user’s manual. Set your multimeter to the capacitor setting, and touch the red and black probes to each of the capacitor’s electrical terminals. If the reading isn’t close to the capacitor’s listed rating, the capacitor needs to be replaced.

    If your capacitor checks out but the compressor won't turn on, the compressor motor is likely bad and should be replaced.

Water Drips From Front Panel

This can be caused by a clogged drain port, clogged drain line, or from a drain pan that isn't properly sloped.

How to Repair a Dripping Air Conditioner

  1. Check the Drain Port

    Inspect the drain port for clogs and remove any visible material. If no visible clog is present, you can verify that the drain port is clear by pouring water down the drain port and seeing if water pools in the pan. If so, you can typically remove the obstruction with a shop vacuum.

  2. Check the Drain Pan

    Use a level to determine if the drain pan is sufficiently sloped for proper drainage. Consult your owner’s manual for the manufacturer’s recommended slope, but the general guideline is to maintain a 1/2-inch slope from the front of the unit to the back. Many drain pans are designed to have the necessary slope when the AC unit is level, which can be verified with a bubble level.

    If following these steps doesn't stop the leak, consider calling a professional.

Air Conditioner Cycles On and Off Too Frequently

This is also called short cycling. An air conditioner that repeatedly turns on and off can be caused by: 

  • A dirty, obstructed, and/or improperly placed thermostat
  • An over- or under-sized air conditioner
  • A dirty air filter
  • A dirty evaporator or condenser
  • A refrigerant leak

How to Fix an Air Conditioner That Turns On and Off Too Frequently

  1. Check the Thermostat

    Ensure that the thermostat is securely clipped onto the evaporator fins, and is free of any dirt or residue. If it’s dirty, carefully unclip it from the evaporator and clean it with a wet rag. Also verify that the thermostat isn’t obstructed by window drapes or other objects.

  2. Examine the Space

    Short cycling can result from your air conditioner being either too large or small for the space you’re using it in. The square-footage a window air conditioner can cool is based on its BTU output. Cross-reference your unit’s BTU output with the square footage of the room it's installed in. If it’s incorrectly sized, you may need to replace it with a unit that has the necessary BTU rating.

  3. Clean the Major Elements of the Unit

    Clean the air filter, evaporator, and condenser.

  4. Look for Drips

    Inspect for signs of a refrigerant leak.

    If following the above steps doesn't fix the problem, consider hiring a professional to make repairs.

Unit Will Not Turn On

If your air conditioner isn’t getting any power, this could be caused by a bad power cord, a bad wall outlet, and a tripped circuit breaker or blown fuse on your home’s main electrical panel.

How to Repair a Window Air Conditioner That Won't Turn On

  1. Examine the Plug

    Make sure the unit’s power cord is well-seated in the wall outlet.

  2. Check the Outlet

    Test the electrical outlet with an appliance that you know works, with a non-contact voltage tester, or with a digital multimeter set to AC volts.  

  3. Consider Replacing the Power Cord

    Unplug the power cord and inspect it for signs of damage or fraying. If so, the power cord should be replaced. 

  4. Check the Breaker (or Fuse) in the Cord

    Check for an integrated circuit break or fuse connected to the power cord. Reset the tripped breaker, or replace the blown fuse.

  5. Check Your Home's Electrical Panel

    Check your home’s main electrical panel to see if a circuit breaker is tripped or a fuse is blown. If so, reset the breaker or replace the blown fuse.

    If, after following these steps, the unit still won't turn on, call a professional to repair it.

Unit Repeatedly Trips Circuit Breaker or Blows Fuses

This can be caused by an improperly sized circuit for your air conditioner, or from the unit overheating from low refrigerant. Most window air conditioners draw between 500 and 1,500 watts of electricity and are designed to run off a 15-amp circuit that can only handle 1,800 watts. For air conditioners on the higher end of that range, the 15-amp circuit may get overloaded if any other devices or appliances are plugged into it. This can cause repeatedly tripped breakers and blown fuses.

How to Fix an Air Conditioner That Trips Circuit Breakers

  1. Reduce the Load on the Circuit

    Unplug or turn off other appliances and devices on the same circuit as your air conditioner. You can determine which wall outlets are on the same circuit by turning off the air conditioner's circuit on your home’s electrical panel and seeing which outlets are no longer receiving power.

  2. Add a New Circuit Breaker

    Install a dedicated circuit breaker and circuit for the outlet your air conditioner plugs into. 

    Warning

    Only a qualified electrician should install a dedicated circuit to your electrical panel.

How to Properly Maintain Your Window Air Conditioner

Maintaining your air conditioner is one of the best things you can do to keep your air conditioner running at its best, and to avoid having to fix it in the first place.

  1. At the Beginning of the Warm Season:

    Prior to firing up your air conditioner for the first time in a while, take the following steps:

    • Clean or replace the filter
    • Inspect and clean evaporator and condenser coils
    • Vacuum out the entire interior of the unit to clear any dust or debris that may have accumulated during the off-season
  2. Monthly While in Use:

    • Clean the filter
    • Inspect the evaporator and condenser, and clean or straighten fins as needed
  3. Every 3 Months While in Use:

    • Replace the filter
  4. At the End of the Warm Season:

    • Perform a deep clean. Remove the air conditioner from the window and take it outside. Remove the face panel and filter to expose the interior. Hose down the face panel, filter, evaporator, condenser, and drain pan. Allow it to dry completely before reassembling.
    • Protect it from the elements. Remove the air conditioner from the window and store in a sheltered location during the off-season, or protect it in its installed location with a commercial window air conditioner cover.