Common Air Handler Problems - Air Handling Unit installed in a tight attic.

With proper maintenance, you can avoid common air handler problems

Common Air Handler Problems - Everyone loves to be comfortable, so when there is a problem with the HVAC system, we can become very uncomfortable. The air handler in the HVAC system has electrical and mechanical components inside it that can experience problems from time to time. Some of the most common problems with air handlers can help you identify the problem and possibly fix the issue — many common air handler problems you can avoid with regular air handler maintenance.

Although some of the issues listed will need the attention of a professional HVAC technician to repair the air handler, after all, an HVAC technician will have all the tools and likely the parts available to make a fast and efficient repair. Furthermore, since every air handler is different it is possible the problems described here do not apply to your situation.

Common Air Handler Problems

Some of the most common problems with air handlers are:

  1. Clear, clean pathway for good airflow
  2. Blower motor failure
  3. Regular filter maintenance

See below for the descriptions and maintenance best practices to avoid these issues:

Clear Duct System and Good Airflow | Common Air Handler Problems

Since the AHU is the central unit that moves the air throughout the ductwork, it is important to make sure nothing obstructs the airflow through the air handler, such as dirty or clogged air filters. A regular air filter maintenance schedule will help you maintain good airflow through the duct system. It also helps keep the air handler components inside clean and free of debris and dust. If you maintain good filter maintenance, you will not have to worry about a dirty evaporator coil or any other components clogging with dust or debris. Furthermore, this includes closing off supply vents.

Dusty and dirty components lead to big problems which can cause your air conditioner to freeze up along with other major issues. Maintaining a good air filter maintenance schedule is easy especially if you have a good digital thermostat. Many of the newer digital thermostats have air filter change reminders. Maintain good filter maintenance and prevent several future problems. Dirty filters can lead to many problems including causing water damage to the home. Finally, the problem can become catastrophic under the worst situations.
Blower motor and squirrel cage

Blower Motor Failure

The next most common problem that can occur with an air handler is a failure of a blower motor, whether it be the blower motor or something else that causes the blower motor to fail. It could be a bad relay, control board, run capacitor, or the blower motor itself. It could also be the blower wheel. These are AHU (Air Handling Unit) problems that need the attention of a professional HVAC technician.

An HVAC technician can identify the problem quickly and make the blower motor repair. It may require ordering parts, or the part may be available on the service truck, but the problem will get resolved quickly and efficiently.

Proper Filter Maintenance | Air Handler Maintenance Procedures | Common Air Handler Problems

Most of the issues described can be avoided with proper filter maintenance. Even the blower motor failure can be enhanced by bad airflow resulting from no regular filter maintenance. It makes the motor work harder, creating more heat and pulling more amperage, which costs you more electricity costs. The dirt from dust that builds up also hurts the motor and creates more heat which can have detrimental effects on the motor. Consequently, the lesson is to keep a good clean filter in the system, and you will reduce any problems that may occur with your air handler.

Air Handling Units  | HVAC Airflow Problems and Troubleshooting | Common Air Handler Problems

filter maintenanceAgain, it is recommended that an HVAC professional do this work. Make sure you read the High Performance HVAC disclaimer before proceeding. A professional will have all the proper HVAC tools to complete the HVAC repair or maintenance job quickly and efficiently. It does not matter what type of equipment you have.

You can have a Trane, Goodman, York, Rheem, or Carrier HVAC system, and it all needs to be maintained. If you decide to do it yourself, make sure you follow the safety procedures as noted on the Air Handler Page about cutting power to the air handling unit before attempting to clean the evaporator coils.

Once you have turned the power supply off to the air handler, open the air handler panel where the suction and liquid lines run into the air handling unit. Be very careful not to bend or crimp these lines or any lines in the air handlers. Another thing to avoid is the fins on the coils. Do not bend them.

That would defeat the purpose of cleaning the coils because it will reduce the amount of air flowing through the coils. Plus, the evaporator fins can cut you. Be careful. Furthermore, check the condensation drain line before you begin this procedure.

Basic Check | Air Handler Maintenance Checklist | Common Air Handler Problems

See the condensate drain section below for more information on this subject. Soak the air handling unit evaporator coil with a soap and water solution. Professionals use an industrial-strength coil cleaner, which may be available at some hardware stores. Let this solution soak for a few minutes. Then take a rag and wipe as much dust off the surface of the evaporator coils as possible. Repeat these steps until the evaporator coils look clean.

Take a flashlight and look between the fins on the evaporator coils. The evaporator fin on the coil should appear to be clean. If not, soak the evaporator coils again and use a brush with light bristles to brush the evaporator coils.

Remove as much dust, dirt, and debris as possible from the evaporator coil. Remember there are two sides to the coil and make sure both sides are clean. The side that will most likely be dirty will be the side where the return airflow comes from. If your evaporator coils are clean and the rest of your air handler components are operating normally you should have a nice cool summer inside your home no matter what the weather is outside.

Checking the Air Handler Blower Motor | Air Handler Maintenance Check

The air handler blower comprises different components in most units. It has an electric motor, a squirrel cage blower wheel, and a cage typically referred to as a squirrel cage. Some air handling units have belt-driven motors, and most have capacitors for the air handler electric motor, and typically, they only required HVAC maintenance on the blower is oiling the air handler blower motor if it has oil ports or checking the belt if you have a belt-driven motor.

Not all blower motors have oil ports. These blower motors use sealed bearings, and never require oil. The air handler blower motors that do have oil ports have little plastic dust caps that are removable so that oil can be applied.

Checking the Air Handler Condensate Lines | Air Handler Leaking in Attic Prevention

Checking the air handler condensate lines is especially important if your air handler is located in the attic. Since the air conditioner evaporator coil (inside the air handling unit) operates at a temperature less than the dew point, it will condense the moisture from the air. This air handling unit coil is designed to allow the moisture to drip into an evaporator condensation pan. Most condensation pans have a 3/4 inch PVC line attached to them that allows the moisture to drain to the outside of the house.

The PVC condensation drain line often becomes clogged with algae and muck. Consequently, it needs to be blown or flushed out from time to time. If your air handler is in an attic, it should have a secondary pan to catch the water in case the primary condensation pan or condensation drain line gets clogged. Typical items that clog condensation lines are algae, muck, and trash, like insulation from the attic. You can treat the evaporator pan and condensation drain lines with algaecide which should work throughout the season.

Prevention of Air Handler Leaks | Troubleshooting | Common Air Handler Problems

For double protection, I recommend that all secondary condensation pans have float switches installed. The float switch will cut the air handling unit off if the secondary condensation pan starts to overfill. That will save you from buying a ceiling from a condensation leak. Your local HVAC service company can install float switches. Check to make sure that the air conditioner condensate line is not plugged. You can do this by pouring water into the air conditioner condensation pan. If it drains fast then the line should be okay.

If it drains slowly or not at all, then the condensation drain line is plugged or beginning to plug. I often find the end of the line outside and take a hose and flush the line. You must be careful if you do this procedure. You can flood the condensation pan and cause water damage. That will clean the line in most cases.

Additionally, you can make sure that the condensation drain line has a downward slant to it. Sometimes people place things in the attic on the condensation drain lines, and it won’t drain. If you’ve checked all that and the condensation water still doesn’t drain properly, you need to call an HVAC professional.

Professional HVAC Technician Maintenance | Air Handler Maintenance

The HVAC professional should have all the necessary HVAC tools to blow the condensation line properly. All of these checks are made by your local Heating and Air Conditioning HVAC company. Just call and ask for a spring tune-up or an HVAC maintenance agreement. A little HVAC preventive maintenance on your HVAC system can save you a lot of money in the future. Take the time to have this HVAC maintenance done and save yourself from the expense and hardship that comes with HVAC breakdowns and HVAC component failure.

In-depth HVAC information:********

HVAC Duct Work should be sealed and insulated. Then the insulation should be sealed to provide a vapor barrier. Commercial HVAC ductwork commissioning requires a pressure test to make sure the ductwork was correctly installed and meets specifications.


*By the time it (HVAC refrigerant) reaches the end of the coils, it should have absorbed enough heat to change it from a liquid to a vapor*. What are the reasons why the coil wouldn’t absorb enough heat to change the state of the refrigerant?

  • Dirty Filters
  • Dirty Coils
  • Collapsed Duct
  • Too many supply vents closed off
  • A bad blower

The bottom line is airflow. There must be the proper amount of airflow across the coils for your system to operate efficiently. Take this one step further. If you have one of the problems mentioned above and the refrigerant remains a liquid, what happens? Refrigerant leaving the evaporator is on a non-stop trip to the compressor. The refrigerant must be changed from a liquid to a vapor before it reaches the compressor. The liquid doesn’t compress and can cause major problems if it reaches the compressor. It’s called liquid slugging and can cause irreparable damage to the compressor.

HVAC Variable Speed Motors | Common Air Handler Problems

Today’s technology, while being more expensive to purchase upfront, can pay for itself over time in energy savings by increasing efficiency. Variable-speed blower motors not only increase efficiency but also increase your comfort. Conventional HVAC systems are designed to maintain comfort based on basic parameters. The parameters include a peak load of 95 degrees Fahrenheit outside temperature with 75 degrees Fahrenheit and 50 percent relative humidity inside.

That means even when the temperature outside is 80 degrees Fahrenheit the system will still operate full blast. It will run as if it were 95 degrees Fahrenheit outside. Imagine you had a car that only did one speed. Sure it would get you there, but how efficient would it be? Both Trane, York, and Carrier HVAC systems have specifically designed systems with variable speed blowers for greater efficiency and humidity removal. Other manufacturers have followed their lead.

Variable Speed ECM Motors Bonuses | Common Air Handler Problems

Variable speed motors (technically called ECM or Electronically Commutated Motor) along with two-stage compressors and multi-stage furnaces offer better control and efficiency. These components and controls help your system runs at the speed it needs to run. The appropriate speed to meet the current load demand. Temperatures are even, and the equipment cycles per hour have an observable reduction. In both the summer and winter, the motor runs at a slower speed until the demand increases. Then it ramps up to meet that higher demand. It only runs or consumes enough energy to meet the current demand. Furthermore, other benefits of having variable-speed motors are:

  • Soft-start capabilities
  • Quieter operation (research indicates up to 50 percent less noise than conventional blowers)
  • Better humidity control adds increased comfort in the summer
  • On higher SEER condensing units, variable-speed motors are used for the condenser fan motor
  • When used in conjunction with multi-stage furnaces the AFUE rating increases

Different manufacturers offer different options with available speeds and control of the variable speed motor. It is important to compare when shopping for new equipment. Use the High Performance HVAC links page to see the different options available from different manufacturers. Variable speed motors used with other high-efficiency options are definitely worth the extra cost of installation. Consequently, it will pay for itself by saving you money in energy costs over the long term.

Conclusion | Air Handler Maintenance

Again, remember that you can have the best, most efficient HVAC machine any manufacturer can design. However, if your ductwork is sub-standard and leaking, you’re losing efficiency. The efficiency you gained by having the best system installed. Ductwork deficiencies are probably the most overlooked problems with an air conditioning and heating HVAC system. Before you spend a ton of money having the best HVAC system installed, check the ductwork. Finally, make sure the ductwork has airtight integrity and is properly insulated.

High Performance HVAC Air Conditioning and Heating Systems  Common Air Handler Problems & Maintenance Schedules

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