General HVAC troubleshooting

Introduction to Troubleshooting

The HVAC Technician’s Vocation

Service technicians earn their living with their troubleshooting skills. Troubleshooting is the process of identifying problems, determining their cause, and correcting the cause of the problem.

Effective troubleshooting requires problem-solving, and the technician needs to do more than try to match symptoms with causes because symptoms have many possible causes. Rather, technicians must understand exactly how the equipment operates so they can analyze the cause of improper operation.

Data collection isn’t troubleshooting

Troubleshooting often requires performing tests on equipment, but taking a lot of readings is not troubleshooting. The data are worthless if they are not understood. Each test should take the technician a step closer to solving the problem.

Not an Easter egg hunt

Bad Capacitor

Most important, troubleshooting is not replacing parts until the system operates. Not only is this approach expensive, but it frequently fails to repair the problem. It is possible to replace all the parts and still have the original problem if the cause is not a defective component.

A step-by-step approach

A methodical approach to troubleshooting that is based on knowledge of fundamental HVAC system operation will result in less time spent overall, less cost in unnecessary replacement parts, and fewer mistakes. Technicians who practice systematic troubleshooting techniques can often correct problems in equipment that they have never seen before.

Written by Jeremy James

Jeremy James is a veteran of the U.S. Navy who has grown his family’s HVAC business into one of the most successful home service businesses in Knoxville, TN. More than 20 years of experience in the HVAC and Engineering industries and passion for what we do has translated into our customer service, professionalism, and quality. LinkedIn

Six Crucial Questions All Service Technicians Must Be Able To Answer

An important part of providing service is answering the customer’s questions. Being prepared to answer questions completely and confidently builds the customer’s confidence in the service technician.

After a troubleshooting call, technicians should be able to answer six general questions:

  • How is the equipment supposed to operate?
  • What is the equipment doing wrong?
  • What is the root cause of the problem?
  • What specific tests or procedures were performed to determine the cause of the problem?
  • How can this be corrected?
  • How much will this cost?

How Is The Equipment Supposed To Operate?

Being able to explain how the equipment is supposed to operate makes explaining what is wrong easier. If the customer perceives that the technician does not understand the equipment, he or she will not have much faith in the technician’s proposed solution.

What Is The Equipment Doing Wrong?

The technician should be able to identify what the equipment is doing wrong. What is the equipment doing that it should not do, or what is it not doing that it should do? Technicians should be able to clearly explain to their supervisors and the customers what is incorrect about the operation of the equipment.

What Is The Cause Of The Problem?

Of course, the customer wants to know exactly what is causing the problem. If possible, explain why this component or situation is causing the problem.

The customer will have more confidence in a cause that can be logically explained. This is where being able to explain the system operation comes in handy.

What Tests Were Performed To Determine The Cause Of The Problem?

Technicians should be able to explain to their supervisor or the customer what specific tests they did. Condemning parts or systems without testing is guessing.

Leaking Air Conditioning Evaporator Coil

Technicians should keep an accurate log of all work performed. Repairing a system by replacing parts is expensive and may not solve the problem! Systems can malfunction for reasons other than bad parts.

An air-conditioning system with a dirty condenser may shut down because of high pressure. This does not mean that the high-pressure switch needs to be replaced or that the system is overcharged. Replacing the high-pressure switch would not affect system operation.

How Can This Be Corrected?

Most customers will not be satisfied with simply finding out why their unit does not work; they want the problem solved. The service technician should be prepared to offer solutions.

Remember that replacing a failed component is not necessarily the solution. Replacing a compressor that has experienced liquid slugging without addressing the cause of the slugging has not solved the customer’s problem. The cause of the liquid slugging must also be found and corrected.

How Much Will This Cost?

A practical reason for recording all tests performed is that this information is generally used to generate bills. Many companies now use service pricing books to calculate the cost of a service call.

Most price books are based on the specific services performed. It is very difficult to produce an accurate bill without a specific list of services performed.

The cost is the foremost question in t he customer’s mind. The service technician needs to be able to address this question, which is certain to be asked.

Many companies now require their technicians to generate and present the bill. Even technicians working for companies that do not generate bills in the field should be prepared to explain the company’s pricing policy.

Systems Approach to Troubleshooting

Technician Maintenance

The processes involved in operating air-conditioning systems include the electrical, refrigeration, airflow, and combustion processes. To make the material manageable, the different processes are often discussed separately.

However, technicians are called to work on the entire system, not an isolated part of it. All system components depend upon each other. In truth, it is difficult to examine any single aspect of system performance while ignoring the rest of the system.

Service technicians must understand the interrelationship between different system components and be aware of the effect one process has on the rest of the system. For example, low evaporator airflow in an air conditioner will cause low suction pressures, causing the compressor to trip out on the low-pressure switch. What may initially look like an electrical problem or a refrigeration problem, may be an airflow problem.

Similarly, refrigeration system problems can have an electrical cause. An inoperative evaporator fan motor can reduce the low-side pressure, but the solution is certainly not more refrigerant.

Stages of Troubleshooting

Troubleshooting can be broken down into several distinct steps, each step logically following the other:

  • Understanding system operational sequence
  • Preliminary system inspection
  • Collecting operational data
  • Recognizing what is operating incorrectly
  • Testing to isolate the cause
  • Recommending corrective action