For proper Air Conditioner Troubleshooting, you need to understand some basics of air conditioners. This includes basic refrigeration, electricity, electrical components and how electro-mechanical controls work. In addition, basic air conditioner components and air conditioner sequence of operation. Before troubleshooting, you need to identify the basic problem with the system. Aside from the basics such as blown fuses or a tripped breaker we will explore other areas to look at for air conditioner troubleshooting. Tripped circuit breakers for air conditioning systems are covered here. A good preventive maintenance program done periodically can help you avoid common air conditioning problems that require troubleshooting.

HVAC Components and Knowledge

Is it a component not working and why is the component not working? In addition, having the proper tools along with knowledge will also help you in troubleshooting air conditioners and fixing problems.

For example, is the compressor working and if the compressor is not working is it the compressor that is bad. Or could it an electro-mechanical component that controls the compressor and motor that is the problem? So in the process of air conditioner troubleshooting, you need to know the basics of air conditioners. You also need to understand basic techniques for troubleshooting different electrical and mechanical aspects of the system as a whole.

Air Conditioner Troubleshooting | HVAC Technical

Airconditioner problem repair
Air Conditioner Troubleshooting HVAC CondensersRecapping Essential Knowledge:

Types of Airconditioners

There are two basic types of central air conditioners. The package system where all the components are in one unit or package. And there are the split system central air conditioning systems. These systems will have the components split from each other and connected via wiring and a refrigeration line set.

Both systems have basically the same components but these components have different configurations. Finding the problem will require understanding these basic components and controls. Whether they are configured in a split system central air conditioning system or a package unit air conditions system.

Components - The Evaporator and Possible Evaporator Problems

AC Repair with evaporator problems

This evaporator coil got limited airflow from old insulation

The Evaporator coil is one of the major components. And depending on the problem that needs repair depends on whether to check the coil in the air conditioner. The evaporator coil receives low-pressure low-temperature refrigerant.

As the refrigerant passes through the coils it absorbs heat from the air that passes over the coils. When troubleshooting you need to check that the coil has the proper amount of airflow across the coils. Airflow first and then refrigerant charge next.

It is also important the proper amount of refrigerant is available inside the evaporator coils. The air conditioner system can be overcharged with too much refrigerant in the system. The same can be applied to heat pumps since heat pumps are air conditioning systems that can also provide heat. Heat pumps provide heating and cooling.

Refrigerant Charge

The air conditioner system can be undercharged (possible refrigerant leak) and not have enough refrigerant. Therefore, you need tools and knowledge of these things to check the charge. Refrigerant leaks are a big problem many people do not fix. If your air conditioning system uses more than 1 pound of charge at any given time it needs to have a refrigerant leak check performed. Finally, remember airflow first and then refrigerant charge. I’ve responded to numerous calls that had dirty clogged air filters and that was the only problem.

Skills for Fixing the Air Conditioner Problem

You need to have the skills and the tools to know the proper charge. With airflow across the evaporator coil in air conditioner troubleshooting, you need to check the air filter to make sure it is not clogged with dirt or debris. Make sure the blower is turning the proper RPM’s and providing the proper amount of flow. It needs to pull (or push) the proper amount of airflow across the evaporator coil.

Too many supply vents closed off can cause airflow problems, therefore creating the issue. It is important that coil has the proper amount of airflow across the coil to ensure the air conditioner is working properly. In finding problems with air-conditioners, this is an essential check of the air conditioner system. Make sure the airflow is good across the coil when looking for air conditioner problems.

Air Flow, Airflow and Air-flow – Air Conditioner Troubleshooting

Any air conditioner relies on proper airflow. The common sense approach for troubleshooting the air conditioner is to check the air flow. Clogged air filters and collapsed ductwork, bad fan motor, and other such problems as described above. These are common things to check before pursuing further issues and wasting your time!

Recap Evaporator Coil Issues:

  • Always make sure you have the proper airflow
  • Check the filters and fan motor, ductwork and too many closed supply vents for restrictions
  • Fan motors need to be checked for proper RPMs. A special tool is needed for this fan motor check. It uses reflective tape and counts the RPM’s as the fan motor is turning.

The Condenser and Possible Condenser Problems | Air Conditioner Troubleshooting

bent fins on condenser coils

Bent Fins on Coil cause air conditioner problems

The condenser coil receives high-pressure high-temperature refrigerant from the compressor. A compressor and condenser can be integral to the condensing unit in a split system.

The compressor and a condenser coil are important components in any type air conditioner system. The refrigerant gas travels from the evaporator coil to the compressor. There is a change from low-temperature low-pressure refrigerant gas to high-pressure high-temperature gas.

Proper training and tools are required to check or troubleshoot the compressor. A basic practice for a compressor is to check the wiring. When checking any electrical components in any type of machinery or mechanical equipment turn off the power and double check it is not powered.

Related Link: Air Conditioner Circuit Board Troubleshooting - Delve Deeper and Learn more about HVAC.

Furthermore, when an air conditioner fails the wires on the compressor can be burned off, therefore causing the problem. Loose electrical connections or corrosion cause compressor failure. Corrosion can cause a loose connection. All electrical connections at the compressor need to be tight. These connections also need to be free of corrosion. When you see what you are dealing with you will understand proper training and tools are a necessity.

Air Flow in the Condenser

Air Conditioner Repair - compressor problemsHermetically sealed compressors are normal in residential condensers and light commercial systems. Therefore, it is difficult to check the internal components of the compressor. The compressor and the condenser coil in air conditioner troubleshooting the condenser coils need the proper amount of airflow.

You need to check the condenser coils for dirt and debris. Remember to turn the power off to the unit before washing the coils. The compressor and the condenser coils work together. The compressor sends the coils hot gas and the coils remove the heat from that gas. The condenser and the compressor work together to make the air conditioner function properly.

Condenser Fan Motors

You should check the condenser air flow. It is necessary to make sure the condenser fan motor is working properly and turning at the proper RPM’s. Designed airflow is important for the condenser coils. If the condenser fan motor is not working at all the AC will not function properly. Therefore, it is possible could cause severe problems and damage the system.

The compressor relies on the fan motor for air flow and without airflow pressures rise. If the fan motor is not working, then it could be a bad motor. A bad capacitor or a bad relay or compressor contactor that controls the fan motor and compressor. Proper knowledge of electro-mechanical controls and electric motor basics will help. It will help you understand the problem much quicker when making repairs to ACs.

Finally, the types of electric fan motors most commonly used in HVAC are PSC motors that utilize capacitors. The air conditioner or heat pump system compressor also very likely uses a capacitor. Some compressors use two capacitors. One run capacitor and one start capacitor. Don’t confuse those with a dual capacitor. A dual capacitor is a capacitor that is a two in one capacitor. It is used for both the condenser fan motor and compressor.

If your air conditioner or heat pump system has a start capacitor it is wired differently than the run capacitors and has a relay to remove it from the compressor circuit after the compressor starts.

Condenser - Essential Component

A condenser is an essential component and if the condenser has problems the air conditioner will not function properly. A condenser is most likely the component where you will find problems.

The condenser is where you will troubleshoot problems with electrical, refrigeration, and some other basic problems. Things like clogged fins in the coils of the air conditioner. Be careful as condensing units and other major components of the air conditioner utilize high voltage that can kill.

Recap for Condensers and Condenser Components:
  1. Be careful!! Doing a thorough check of the electrical system and components in the condenser is necessary. Caution!!! High Voltage!! Only a properly trained technician should perform these checks and do so carefully.
  2. A compressor check and a check of the refrigeration system.
  3. Basic knowledge of refrigeration and refrigeration components is necessary to determine the proper refrigerant charge.
  4. Compressors and condenser coils work together.
  5. Compressors and condensers problems can affect one or the other component and need to be repaired.
  6. There are two types of air conditioner systems: The split systems and the package unit.
HVAC Refrigeration

Basic Air Conditioner Refrigeration Component Diagram

Controls and Control Problems – Air Conditioner Troubleshooting

circuit board problems cooling

Circuit Board for an Air Conditioner

A Compressor Contactor is an HVAC Control. When seeking problems with air conditioning systems you need to understand basic air conditioning controls.

Controls include the thermostat and any relays or contactors in the air conditioner system. Thorough knowledge and understanding of these components and devices will make the process easier for the technician. It is also a good thing to understand other HVAC circuit basics such as Ohms Law.

Air Conditioner Circuit Boards

These basic circuit principles help you understand electrical problems easier. Many modern air conditioning systems use printed circuit boards for control. Some components, however, are still contactors and relays. These components control fan motors and the compressor in the air conditioner system.

Technicians can find problems with the air conditioning control circuit board easily. A circuit board can appear to be confounding to the vast majority. After all, it is a control circuit board. There are rules to follow in troubleshooting basic HVAC circuits. One is that the circuit board needs a source of power and the source typically comes from the transformer.

When powered it will have a sequence of operation or an order of operations. This is based on input from the thermostat and any safety circuits in the air conditioner system.

Check the input voltage and based on the sequence of operation you check the output. Input is important and mandatory for proper function of the circuit. If no input, then you need to check the source and fix that before proceeding.

If you have input to the board and no output, then you need to check why there is no output. Check the safety circuit. If no problems are found with the safety circuit move on to the circuit board. The problem could be on the board and needs to be looked at carefully.

Control Voltage and Control Circuits – Air Conditioner Troubleshooting

Maybe there is a problem with the circuit board or the safety circuit is open somewhere. That will prevent the output from occurring and the unit from operating. With relays and contactors in air conditioner troubleshooting, you need to understand that something is controlling the relay or contactor. The relay or contactor has a function to either open or close. This is based on the control voltage and where the control voltage originates. You can use the hopscotch method with your multimeter to fond problems in the circuit provided you understand control circuits.

The origin of the control voltage in most residential HVAC systems originates from the step-down transformer. You will find the transformer in the equipment somewhere. It is important to understand the step-down transformer and how it works.

As with the circuit board above. If you have input but no output, therefore something is wrong with the component. In this case, it is a control step-down transformer. Does the HVAC system have one or two transformers? Air Conditioner troubleshooting requires one to know these answers and how to answer the questions and solve the problem.

Almost all relays and contactors in a typical air conditioner system are controlled by the thermostat. When the thermostat calls for air conditioning it closes some contacts in the thermostat. This completes the circuit for the control voltage.

That process sends the control voltage to either a relay or a contactor or both. When the relay or contactor or both close the contacts inside the relay or contactor close. This completes another circuit which is typically line voltage but can be a control circuit. This line voltage energizes compressors and fan motors and the system starts. And the control voltage controls many other components including relays and contactors.

Reading Ladder Logic Diagrams

As a result of learning ladder logic, you will understand the sequence of operation. The sequence as designed by the engineer and the manufacturer. This makes the air conditioning problem-solving process becomes simpler because of that understanding.

That is if the air conditioner comes with a ladder logic diagram. Many air conditioners do not come with a ladder logic diagram but most noteworthy, a component pictorial diagram. A good technician can take a pictorial diagram and draw their own ladder logic diagram. In doing that you can better understand the sequence of operation of the air conditioner system.

Maintenance Tips to Avoid Air Conditioner Troubleshooting
  • A basic checklist for any central air conditioner troubleshooting will include checking for blown fuses or tripped circuit breakers.
  • Heating and cooling systems NEED preventive maintenance. Preventive maintenance will help avoid serious problems by taking care of little problems. Little problems that turn into big problems.
  • A good air filter maintenance keeps the system running smoothly and makes your central air conditioner more energy efficient. It also enhances indoor air quality. Besides, having a dirty air filter could result in an air conditioner repair call and that would cost you money. More money than it would take to change that air filter. Home cooling systems require good airflow so make sure your preventive maintenance is regular and includes keeping those air filters clean. That advice includes heat pump systems also. Never automatically assume you have a low refrigerant charge before checking the filters and supply vents for proper airflow.
  • As always be careful with any electrical repair. Air conditioning systems use high voltage (and low voltage). Electrical repair on any heating and cooling system needs to be done by someone familiar with electrical safety. Be careful!!!
  • If your heating system is a gas furnace be careful working around the gas furnace. Remember, a gas furnace utilizes a volatile explosive gas and can be dangerous if there is a leak. The goes in line with the electrical repairs above.
Troubleshooting Tips
  • Access panels on air handlers usually have safety switches. If you remove the access panel for an air handler or a gas furnace you will likely kill power to the unit. If the access panel is not replaced properly then you could have problems with the system not working.Make sure you reinstall the access panel for your air handler or gas furnace properly if you remove it.
  • Even a common air conditioner repair will require you to have common air conditioner repair tools.  Nut drivers, a basic set of wrenches, pliers and other basic tools for air conditioner repair. Other advanced tools include a multi-meter for reading electrical circuits and testing for a blown fuse. For a low refrigerant charge, you will need a set of compound refrigeration gauges. Additionally, for low refrigerant charges, you will need a pressure-temperature chart and basic knowledge of refrigeration and a license to handle refrigerants. Low refrigerant charges are tricky and sometimes will require a professional to troubleshoot the problem.
  • Whether you have a central air conditioner or a heat pump all these tips can apply. Heats pumps have additional components than air conditioners but run on the same principles. The difference is that heat pump systems are heating systems and cooling systems. Whereas an air conditioner only offers home cooling.
  • Finally, when using your lawn mower around a condenser unit turn the condenser unit off. A lawn mower will throw grass up into the condenser coils. This causes a blockage and results in higher head pressures. So when the lawn mower is around the condenser avoid problems by turning the condenser off. Keeping the condenser clean will also make the condenser unit more energy efficient. The same as changing those dirty filters for indoor air quality and good airflow.

Air Conditioner Troubleshooting Conclusion

Finally, the bottom line to finding and fixing air conditioner problems is to understand the basic components of the system. Then break the system down into parts and look for problems. When seeking problems with air conditioning a good technician can easily and quickly identify problems. They quickly identify the part of the system which is causing the failure and make appropriate repairs to the system.

Much of this comes from learning the air conditioning system basic knowledge and part of it comes from field experience. Taking a course in HVAC and AC controls and refrigeration will help you, therefore you need to study. It will help you understand these processes and make you more efficient at repairing air conditioners.

Additionally, don’t forget to follow good maintenance tips to prevent problems in the first place. A dirty air filter and clogged condenser coils are not friends of a good energy efficient heating and cooling system.

High Performance HVAC

Air Conditioner Troubleshooting | HVAC Technical