How to Troubleshoot like an Expert

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A Systematic Approach

By Warren Rhude

To expertly troubleshoot electrical equipment, problems must be solved by maintenance, replacing only defective equipment or components in the least amount of time. One of the most important factors in doing this is the approach used. An expert troubleshooter uses a system or strategy to logically and systematically analyze a circuit and determine exactly what is wrong.

The approach described here is a logical, systematic approach called the 5-Step Troubleshooting Approach. It is a proven process that is highly effective and reliable in helping to solve electrical problems.

This approach differs from troubleshooting procedures in that it does not tell you step-by-step how to troubleshoot a particular kind of circuit. It is more of a thinking process used to analyze a circuit's behavior and determine the components responsible for the faulty operation. This general approach allows it to be used on any electrical circuit. Electricians and maintenance can apply the principles covered in this approach to many other types of problem-solving scenarios, not just electrical circuits.

The 5-Step Troubleshooting Approach consists of the following:

Preparation
Step 1 Observation
Step 2 Define Problem Area
Step 3 Identify Possible Causes
Step 4 Determine Most Probable Cause
Step 5 Test and Repair
Follow-up

Let's take a look at these in more detail.

Preparation

Before troubleshooting any equipment, you must be familiar with your organization's safety rules and procedures for working on electrical equipment. These rules and procedures govern the methods you can use to troubleshoot electrical equipment (including lockout/tagout procedures, testing procedures, etc.) and must be followed while troubleshooting.

Next, you need to gather information regarding the equipment and the problem. Be sure you understand how the equipment is designed to operate. It is much easier to analyze faulty operation when you know how it should operate. Operation or equipment manuals and drawings are great information sources and helpful to have available. If there are equipment history records, you should review them to see if there are any recurring problems. You should also have any documentation describing the problem on hand. (i.e., a work order, trouble report, or even your notes taken from a discussion with a customer.)

Step 1 - Observe

Most faults provide obvious clues as to their cause. Through careful observation and a little bit of reasoning, most faults can be identified as to the actual component with minimal testing. When observing malfunctioning equipment, look for visual signs of mechanical damage, such as indications of impact, chafed wires, loose components, or parts lying in the bottom of the cabinet. Look for signs of overheating, especially on wiring, relay coils, and printed circuit boards.

Remember to use your other senses when inspecting equipment. The smell of burnt insulation is something you won't miss. Listening to the sound of the equipment operating may give you a clue as to where the problem is located. Checking the temperature of components can also help find problems, but be careful while doing this; some components may be alive or hot enough to burn you.

Pay particular attention to areas identified either by past history or by the person who reported the problem. A note of caution here! Do not let these mislead you; past problems are just that, past problems, and they are not necessarily the problems you are looking for now. Also, take reported problems as something other than fact, and always check for yourself if possible. The person reporting the problem may have described it differently or may have made their own incorrect assumptions.

When faced with equipment which is not functioning properly you should:

• Be sure you understand how the equipment is designed to operate. When you know how it should operate, it makes it much easier to analyze faulty operations.
• Note the condition of the equipment as found. It would be best to look at the state of the relays (energized or not), which lamps are lit, which auxiliary equipment is energized or running, etc. This is the best time to inspect the equipment (using all your senses) thoroughly. Look for signs of mechanical damage, overheating, unusual sounds, smells, etc.
• Test the operation of the equipment, including all of its features. Make a note of any feature that is not operating correctly. Make sure you observe these operations very carefully. This can give you a lot of valuable information regarding all parts of the equipment.

Step 2 - Define Problem Area

At this stage, you apply logic and reasoning to your observations to determine the problem area of the malfunctioning equipment. Often, when equipment malfunctions, certain parts will work properly while others will not.

The key is to use your observations (from step 1) to rule out parts of the equipment or circuitry that are operating correctly and not contributing to the cause of the malfunction. You should continue to do this until you are left with only the part(s) that, if faulty, could cause the symptoms that the equipment is experiencing.

To help you define the problem area, you should have a schematic diagram of the circuit in addition to your noted observations. Starting with the whole circuit as the problem area, take each noted observation and ask yourself, "What does this tell me about the circuit operation?" If an observation indicates that a section of the circuit is operating correctly, you can eliminate it from the problem area. Identify each part of the circuit from the problem area as you eliminate them on your schematic. This will help you keep track of all your information.

Step 3 - Identify Possible Causes

Once the problem area(s) have been defined, it is necessary to identify all the possible causes of the malfunction. This typically involves every component in the problem area(s).

It is necessary to list (actually write down) every fault that could cause the problem, no matter how remote the possibility of it occurring. Use your initial observations to help you do this. During the next step, you will eliminate those which are not likely to happen.

Step 4 - Determine Most Probable Cause

Once the list of possible causes has been made, it is then necessary to prioritize each item as to the probability of it being the cause of the malfunction. The following are some rules of thumb when prioritizing possible causes.

Although it could be possible for two components to fail simultaneously, it is not very likely. Start by looking for one faulty component as the culprit.

The following list shows the order in which you should check components based on the probability of them being defective:

• First, look for components that burn out or have a tendency to wear out, i.e., mechanical switches, fuses, relay contacts, or light bulbs. (Remember that in the case of fuses, they burn out for a reason. You should find out why before replacing them.)
• The next most likely cause of failure are coils, motors, transformers, and other devices with windings. These usually generate heat and, with time, can malfunction.
• Connections should be your third choice, especially screw type or bolted type. Over time, these can loosen and cause a high resistance. In some cases, this resistance will cause overheating and eventually burn open. Connections on equipment subject to vibration are especially prone to coming loose.
• Finally, it would be best if you looked for defective wiring. Pay particular attention to areas where the wire insulation could be damaged, causing short circuits. Don't rule out incorrect wiring, especially on a new piece of equipment.

Step 5 - Test and Repair

Testing electrical equipment can be hazardous. The electrical energy contained in many circuits can be enough to injure or kill. Ensure you follow all your company's safety precautions, rules, and procedures while troubleshooting.

Once you have determined the most probable cause, you must either prove it to be the problem or rule it out. This can sometimes be done by careful inspection; however, in many cases, the fault will be such that you cannot identify the problem component by observation and analysis alone. In these circumstances, test instruments can be used to help narrow the problem area and identify the problem component.

There are many types of test instruments used for troubleshooting. Some are specialized instruments designed to measure various behaviors of specific equipment, while others, like the multimeters, are more general and can be used on most electrical equipment. A typical multimeter can measure AC and DC Voltages, Resistance, and Current.

An essential rule when taking meter readings is to predict what the meter will read before taking the reading. Use the circuit schematic to determine what the meter will read if the circuit is operating normally. If the reading is anything other than your predicted value, you know that the fault affects this part of the circuit.

Depending on the circuit and type of fault, the problem area, as defined by your observations, can include a large area of the circuit, creating a massive list of possible and probable causes. Under such circumstances, you could use a 'divide and eliminate' testing approach to eliminate parts of the circuit from the problem area. The results of each test provide information to help you reduce the size of the problem area until the defective component is identified.

Once you have determined the cause of the faulty circuit operation, you can proceed to replace the defective component. Be sure the circuit is locked out, and you follow all safety procedures before disconnecting the component or any wires.

After replacing the component, you must test and operate all features of the circuit to be sure you have replaced the proper component and that there are no other faults in the circuit. It can be embarrassing to tell the customer you have repaired the problem only to have him find another problem with the equipment just after you leave.

Testing is a large topic, and this article has only touched on the highlights.

Follow up

Although this is not an official step of the troubleshooting process, it should be done once the equipment has been repaired and put back in service. It would be best to try to determine the reason for the malfunction.

• Did the component fail due to age?
• Did the environment in which the equipment operates cause excessive corrosion?
• Are there wear points that caused the wiring to short out?
• Did it fail due to improper use?
• Is there a design flaw that causes the same component to fail repeatedly?

Through this process, further failures can be minimized. Many organizations have their own follow-up documentation and processes. Make sure you check your organization's procedures.

Adopting a logical and systematic approach such as the 5-Step Troubleshooting Approach can help you troubleshoot like an expert!

About the Author:
Warren Rhude is president of Simutech Multimedia Inc., An e-learning company that develops computer-based training simulations for electrical troubleshooting. Warren has an electrical background and has taught troubleshooting for several years at a prominent electrical utility.

Publishers Note:

Simutech Multimedia developed a series of award-winning simulations for learning electrical troubleshooting skills. We helped Warren develop the PLC troubleshooting part of the software and made the software known globally through sales and marketing on our site. Warren sold the company a few years back, and that software is no longer available for individuals to purchase.

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