Making the correct diagnosis requires skill and patience on behalf of the HVACR service technician. Much as a doctor performs tests to gather clues about a patient’s ailment, service technicians use tools and procedures to accurately pinpoint why an HVACR system will not function properly. The principles guiding these troubleshooting steps are universal, even if their implementation is not. Technicians and instructors may vary on the proper practice of these skills, but they all agree that troubleshooting and diagnostics are required skills for every technician.



Gary Xavier is an author and instructor who developed a five-step troubleshooting routine 20 years ago and has been using and teaching it successfully ever since. The current owner of On-Site Consulting Service, Ovid, New York, he has authored 14 HVACR textbooks, including his latest one, “Math for HVACR,” published by Goodheart-Wilcox Publisher Inc.

“Because all people learn and understand a bit differently, what works for one may not exactly work for another technician,” said Xavier. “But there are fundamental concepts that work for everyone, and that is what I try to convey in my training, because troubleshooting is a skill that has to be acquired by each technician in their own manner.”

His five routines are observation, logical thinking, establishing a pattern, accepting help, and practice.

FUNDAMENTALS: Gary Xavier, author and instructor, developed this five-step troubleshooting routine 20 years ago. He has been teaching it ever since.

1. Observe

Observation sets the tone for how a technician approaches the problem. According to Xavier, it forces techs to take a look at the big picture, pushing them out of parts changer into troubleshooter mode. The approach includes looking for obvious things to help in diagnosis.

“If the unit is not operating at all, start with the electrical supply and work from there,” he said. “If the unit is operating but not performing properly, then start by determining exactly what the system is doing incorrectly. Look before you touch.”


2. Think Logically

According to Xavier, if it is an air conditioning issue, technicians should review the refrigeration cycle. If it is a heating system, he suggested they think about both the process of changing energy from fuel to heat, as well as the sequence of ignition for the burner.


3. Establish a Pattern

Having figured out what process and flow works best for them, Xavier tells his students and contractors to repeat this process the same way all the time.

“This will eliminate missed steps and streamline the troubleshooting process,” he said. “Do not deviate from your pattern.”


4. Accept Help

This help is not just from an instructor or fellow technician. Xavier expressed the importance of the help that every manufacturer provides in written troubleshooting guides. He reminded technicians that manufacturers want their equipment to work properly.

“They will typically also try to help when they are asked,” he added.


5. Practice

Repetition is key.

“It takes years to see all of the potential problems that may be encountered in the field, and even then, as equipment and controls change, a technician has to be constantly learning.”



Jason Obrutz is a content developer at ESCO Group/HVAC Excellence, as well as the former director of education and lead instructor at the HVAC Technical Institute in Chicago. His top five diagnostic tips are be safe, start at the beginning, always check the thermostat, look and listen, and determine if the problem is mechanical or electrical.

BEST PRACTICES: Jason Obrutz, content developer at ESCO Group/HVAC Excellence, offers these five diagnostic tips.

1. Be Safe

Obrutz challenges technicians to make safety a primary concern and believes it should be expressed in both training and company standards.

“Dangers lurk in the form of high voltage, charged capacitors, pressurized refrigerant lines, gas-carrying lines, combustion gases, confined spaces, etc.,” he said. “Don’t rush or hurry through a job, or you might wake up dead.”


2. Start at the Beginning

When technicians arrive at calls, they often already have a few thoughts as to what is wrong. This can pigeonhole them into a diagnosis before they have done anything with the equipment, said Obrutz.

“Start at the beginning with an open mind,” he said. “Listening to the equipment owner can provide a great deal of information about the system. I advise techs to observe the symptoms for themselves.”


3. Always Check the Thermostat

It can be a common practice for technicians to go straight past the control on the wall and head to the primary heating and cooling equipment. This action, however, assumes that the equipment owner knows how to operate the thermostat properly, which isn’t always the case.

“There may be a pre-existing program or improperly set operating parameter that is causing the undesired operation,” said Obrutz. “This is especially the case with the newer, internet-capable thermostats and controls.”


4. Look and Listen

Common sense can help guide technicians through proper diagnostics, but using some of their five senses will also help provide clues as to what is actually wrong with a system.

“What is the system telling you? What do you hear? What do you not hear?” Obrutz asked. “Are there any noises or smells coming from the system?

“Using the power of operation in the early stages of troubleshooting can help to shorten the overall time necessary to find the problem,” he added.


5. Determine if it’s Mechanical or Electrical

Obrutz explained that most system problems can be divided into two categories — mechanical or electrical.

Understanding which one can help technicians choose the correct tools as well as narrow down the cause of the malfunctioning equipment.

“A digital multimeter is necessary to diagnose a bad transformer or contactor, but it is not necessary to diagnose a broken fan blade, loose belt, or low gas pressure,” he said. “Recognizing the differences and having the right tools for the right job are a necessity for success.”



Like Xavier, Obrutz acknowledges that people learn differently, but Obrutz underscored his diagnostic tips with the importance of understanding schematics and sequence of operation. Equipment diversity in the field keeps most technicians from memorizing these elements, but being able to read and understand a system wiring diagram is one of the most important skills a technician can have, according to Obrutz.

“The sequence of operations for any system can be determined by reading the system wiring diagram,” he said. “Troubleshooting any system goes a lot quicker and smoother when its sequence of operations is understood.”

Publication date: 1/28/2019

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