Air Conditioner Troubleshooting | HVAC Technical
Air Conditioner Troubleshooting
- To properly troubleshoot air conditioners
one needs to understand some basics of air conditioners including basic refrigeration
, electricity, electrical components
and how electro-mechanical controls work, basic air conditioner components and air conditioner sequence of operation
. Before troubleshooting air conditioners you need to identify the basic problem of the air conditioner. Is a component not working and why is the component not working. For example, is the compressor working and if the compressor is not working is it the compressor that is bad
or is it an electro-mechanical component that controls the compressor with the problem that will prevent the air conditioner from running? So in the process of troubleshooting air conditioning not only do you need to know the basics of air conditioners you also need to understand basic techniques for troubleshooting air conditioners.
Recapping Essential Knowledge for Properly Troubleshooting Air Conditioners:
- Refrigeration Knowledge
- Electricity Knowledge
- Electrical Components and How these Components Works
- And Air Conditioner Sequence of Operation
Air Conditioner Troubleshooting - Air Conditioner Types
There are two basic types of central air conditioners
. The package system air conditioner where all the components for the air conditioner are in one unit or package and there is a split system air conditioner where some of the components are split from each other but connected via wiring and a refrigeration line set. Both systems have basically the same air conditioner components but these components have different configurations. Finding the problem with the air conditioner will require understanding these basic components whether they are configured in a split system air conditioner or a package unit air conditioner.
Recap Air Conditioning Systems Covered for this Article:
- Air Conditioners can be either split system air conditioners
- or they can be package unit air conditioners
Air Conditioner Troubleshooting – Components
The Evaporator and Possible Evaporator Problems
The Evaporator coil
is a one of the major components and depending on the problem which needs air conditioner troubleshooting
depends on the necessity to check the evaporator coil in the air conditioner. The air conditioner evaporator coil receives low pressure low temperature refrigerant. As refrigerant passes through the evaporator coils it absorbs heat from the air that passes over the coils. In air conditioner troubleshooting it is important to check that the evaporator coil has the proper amount of designed air flow across the coils. It is also important the proper amount of refrigerant is available inside the evaporator coils. The air conditioner system can be overcharged and too much refrigerant will be in the coils or the air conditioner system can be undercharged (possible refrigerant leak) and not have enough refrigerant. In either case, if you are looking for the problem with an air conditioner you will need to have the skills and the tools to know what a proper charge is for an air conditioner system. With airflow across the evaporator coil in air conditioner troubleshooting you need to check the filter to make sure it is not clogged with dirt or debris
. Make sure the blower is turning the proper RPM’s so that it pulls (or pushes) the proper amount of airflow across the evaporator coil. Too many supply vents closed off can cause air flow problems. It is important that evaporator 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 evaporator coil when looking for air conditioner problems.
Since air flow is important for the proper function of the air conditioner a common sense approach to troubleshooting the air conditioner is to check the air flow. Clogged air filters
, collapsed duct work, bad fan motor
, and other such problems as described above are the common things to check before pursuing further issues!
Recap Evaporator Coil Issues:
- Always make sure you have the proper air flow
- Check the fan motor, filters, duct work, or closed supply vents for restrictions of air flow
Air Conditioner Troubleshooting - The Condenser and Possible Condenser Problems
The condenser coil
receives high pressure high temperature refrigerant from the compressor. The compressor and the condenser can be integral to the condensing unit in a split system. Whether it is a split system AC or a package unit air conditioner the compressor and the condenser coil are important components in an air conditioner system. The refrigerant gas travels from the evaporator coil to the compressor where it is changed from a low temperature low pressure refrigerant gas to high pressure high temperature gas.
In troubleshooting air conditioners there is not much the layman can do to check or troubleshoot the compressor
without the proper tools. A basic air conditioner troubleshooting practice for a compressor is to check the wiring. Of course when checking any electrical components in any type of machinery or mechanical equipment is to disconnect or turn off the power to the equipment. In some cases the when an air conditioner fails the wires on the compressor could be burned off. In troubleshooting any HVAC equipment wires can be burned off because of a loose electrical connection or corrosion
. Corrosion can cause a loose connection. It is important any loose electrical connections and corrosion be cleaned and terminated properly to the compressor terminals.
Since nearly all residential and light commercial compressors are hermetically sealed there is not much else you can do if there is a problem with the compressor when finding problems with air conditioners. Going from the compressor to the condenser coil in air conditioner troubleshooting it is important the condenser coils have the proper amount of airflow flowing through the condenser coils. Many times in troubleshooting air conditioning the condenser coils are plugged by dirt and debris and need to be cleaned. Turning the power off to the unit before washing the coils is advised. When troubleshooting the air conditioner condenser airflow of the condenser it is also important to make sure the condenser fan motor
is working properly and turning at the proper RPM’s so the designed airflow is being pulled through the coils. If the condenser fan motor is not working at all the AC will not function properly and it is possible you could cause severe problems with the compressor. If the fan motor is not working then it could be a bad motor 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 understand the problem much quicker when making repairs to AC's.
The condenser is an essential component for the air conditioner and if the condenser has problems the air conditioner will not function properly. The condenser is most likely the component of the air conditioner where one will troubleshoot problems with electrical, refrigeration, or some other basic problem like clogged fins in the coil 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:
- Be careful but 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.
- A compressor check and a check of the the refrigeration system is needed to troubleshoot air conditioners.
- Basic knowledge of refrigeration is necessary to determine the proper refrigerant charge for the air conditioner.
Air Conditioner Troubleshooting - Air Conditioning Controls and Air Conditioner Control Problems
Compressor Contactor is an HVAC Control. When seeking problems with air conditioning systems it is very good that a highly skilled technician understands basic air conditioning controls. From the thermostat to any relays or contactors in the air conditioner system a thorough knowledge and understanding of these components and devices will make the air conditioning troubleshooting process easier for the technician. It is also a good thing to understand other HVAC circuit basics such as Ohms Law
. These basic circuit principles help you understand electric problems easier. Many modern air conditioning systems use printed circuit boards for control of some components however there are still contactors and relays in the system that control fan motors and the compressor in the air conditioner system. Finding a problem air conditioning control is really easy even though it looks or appears to be a complicated thing when looking at a control circuit board. One basic rule of troubleshooting a basic HVAC circuit
is that the circuit board needs a source of power and that when powered it will have a sequence of operation based on input from the thermostat and any safety circuits in the air conditioner system. You check the input voltage and based on the sequence of operation you check the output. If you do not have input to the board then you need to check the source and fix that before proceeding. If you have input to the board but no output then you need to check why there is no output.
Air Conditioner Troubleshooting | HVAC Technical - Control Voltage
Perhaps there is a problem with the board or the safety circuit is open somewhere which will prevent the output from occurring. With relays and contactors in air conditioner troubleshooting you need to understand that something is controlling the relay or contactor with control voltage and that the relay or contactor has a function to either open or close based on the control voltage and where the control voltage comes from.
The origin of the control voltage in most residential HVAC systems comes from a step-down transformer located in the unit 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 then 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 or how to answer the questions.
For the most part 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 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 completing another circuit which is typically line voltage. This line voltage energizes compressors and fan motors and the system starts.
Air Conditioner Troubleshooting | HVAC Technical - Ladder Logic
If one was to learn ladder logic then one can understand the sequence of operation as designed by the design engineer and the air conditioning problem solving process becomes simpler. That is if the air conditioner comes with a ladder logic diagram. Many air conditioners do not come with a ladder logic diagram but with a component pictorial diagram. A good technician can take a pictorial diagram and draw their own ladder logic diagram so they can better understand sequence of operation for the air conditioner system.
Air Conditioner Troubleshooting Conclusion
The bottom line to finding and fixing air conditioner problems is to understand the basic components of the system and then break the system down into parts. When seeking problems with air conditioning a good technician can easily and 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 system and part of it comes from field experience. Taking a course in HVAC and AC controls and refrigeration will help you understand these processes and make you more efficient at repairing air conditioners.
Other Air Conditioner Troubleshooting resources can be found here
Air Conditioner Troubleshooting | HVAC Technical