One of the most difficult things a new air conditioning technician faces is troubleshooting a broken air conditioner or heat pump is coming up with a systematic process.

An AC system can malfunction for many reasons:

  • Mechanical parts and contacts can wear out
  • Wires can overheat and short out or burn open
  • Equipment can be damaged by impact or vibration
  • Equipment is operating in conditions it was not meant to operate in

To expertly repair an air conditioner, the problem must be solved by identifying and replacing the defective components.  By using a systematic approach to troubleshooting, it brings order and helps you logically analyze the fault.

A logical and systematic approach to AC repair can be broken down into 5-Steps. What I describe here is the process not how to troubleshoot a particular problem.  Here are the steps:

  • Preparation
  • Observation
  • Define the problem area
  • Identify possible causes
  • Determine the most probable cause
  • Repair and test
  • Follow-up

1 – Preparation

Before you begin troubleshooting any heat pump or air conditioning system, you must first remember safety. Next, you must gather the information about the equipment you’re working on. It is much easier to analyze a problem if you understand how the system is supposed to work. Locate and review equipment manuals and consult with the homeowner on the repair history of the system. Trane has a great Service Facts sheet located on the inside cover of the outdoor unit.

2 – Observation

Many air conditioning failures have obvious clues as to their cause.  Careful observation of the system operation, many times, can identify the fault with very little testing.  Look for burnt or broken wires, oil in the bottom of the cabinet, swollen capacitors.  Use your senses, a burnt transformer smells, the sound of the equipment gives you clues. The temperature of components can also help identify problems. Many times the homeowner will help identify the problem. Do not assume anything.

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3Get Out Your Tools

At this stage you should have a good idea where to start checking for problems. Step 1 is often used to rule out what isn’t wrong. Study the schematic diagram or follow the manufacturer’s troubleshooting guide. As you test each component, ask yourself, “What does this tell me about the problem?” Note your observations and readings.  Often times, you can find out what the problem is by identifying what is working right.

Tip – Before making a voltage, pressure, or temperature reading – try to predict what it should read from studying the wiring diagram and reviewing refrigeration principles.

4 – Identify Possible Causes

Once you have found the problem, it is extremely important to identify the cause. Just fixing the problem without identifying the cause will lead you to future unhappy customers. Was it vibration, abrasion, corrosion, lack of maintenance, or age of the component? Identify the cause and take care of it as well.

 5 – Repair and Re-test

After identifying and repairing the faulty component, test and operate the system for a complete cycle. This will make sure you have replaced the proper component and no other components are faulty. It is very embarrassing to tell the customer you have fixed their problem, only to be called out the next day because their air conditioner isn’t working again.

by Ron Walker


Ron Walker
Ron Walker

After retiring from the U.S. Marines and achieving his B.S. degree, Ron Walker entered the HVAC field. He has been an HVAC technician, service manager, and business owner. Working as a service manager, he spent many years training HVAC technicians to be more technically competent and really understand their trade. His passion for teaching and helping others resulted in the creation of HVAC Training Solutions, LLC.