How to Troubleshoot like an Expert
to Troubleshoot like an Expert
By Warren Rhude
To expertly troubleshoot electrical equipment, problems must be solved by
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 approach that allows them 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 that is used to analyze a circuit’s behavior and
determine what component or components are responsible for the faulty operation.
This approach is general in nature allowing it to be used on any type of
In fact, the principles covered in this approach can be applied to many other
types of problem solving scenarios, not just electrical circuits.
The 5 Step Troubleshooting Approach consists of the following:
Step 1 Observation
Step 2 Define Problem Area
Step 3 Identify Possible Causes
Step 4 Determine Most Probable Cause
Step 5 Test and Repair
Let’s take a look at these in more detail.
Before you begin to troubleshoot any piece of 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 your 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 sources of information and
are 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 on-hand any documentation describing the problem. (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 very little testing. When observing malfunctioning
equipment, look for visual signs of mechanical damage such as indications of
impact, chafed wires, loose components or parts laying in the bottom of the
cabinet. Look for signs of overheating, especially on wiring, relay coils, and
printed circuit boards.
Don't forget 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 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
Pay particular attention to areas that were identified either by past history
or by the person that reported the problem. A note of caution here! Do not let
these mislead you, past problems are just that – past problems, they are not
necessarily the problem you are looking for now. Also, do not take reported
problems as fact, always check for yourself if possible. The person reporting
the problem may not have described it properly or may have made their own
When faced with equipment which is not functioning properly you should:
- Be sure you understand how the equipment is designed to operate. It makes
it much easier to analyze faulty operation when you know how it should
- Note the condition of the equipment as found. You should 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 give the
equipment a thorough inspection (using all your senses). Look for signs of
mechanical damage, overheating, unusual sounds, smells etc.;
- Test the operation of the equipment including all of its features. Make
note of any feature that is not operating properly. 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
It is at this stage that you apply logic and reasoning to your observations
to determine the problem area of the malfunctioning equipment. Often times when
equipment malfunctions, certain parts of the equipment will work properly while
The key is to use your observations (from step 1) to rule out parts of the
equipment or circuitry that are operating properly 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
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
appears to be operating properly, you can then eliminate it from the problem
area. As you eliminate each part of the circuit from the problem area, make sure
to identify them on your schematic. This will help you keep track of all your
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 which 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
Although it could be possible for two components to fail at the same time, 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 which 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
- 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 will burn open.
Connections on equipment that is subject to vibration are especially prone
to coming loose.
- Finally, you should look for is 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. Make sure you follow
all your companies safety precautions, rules and procedures while
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
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 in nature and can
be used on most electrical equipment. A typical multimeter can measure AC and DC
Voltages, Resistance, and Current.
A very important 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 this part of the circuit
is being affected by the fault.
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 very large
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 provides 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 operation of the circuit 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
After replacing the component, you must test 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 very embarrassing to tell the customer
that you have repaired the problem only to have him find another problem with
the equipment just after you leave.
Please note, Testing is a large topic and this article has only touched
on the highlights.
Although this is not an official step of the troubleshooting process it
nevertheless should be done once the equipment has been repaired and put back in
service. You should try to determine the reason for the malfunction.
- Did the component fail due to age?
- Did the environment the equipment operates in 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
Adopting a logical and systematic approach such as the 5 Step
Troubleshooting Approach can help you to 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.
Multimedia has developed a series of award winning simulations for learning
electrical troubleshooting skills. Click here for more
information on these programs or to download
a free demo.
UP-TIME Publications teaches your maintenance crew engineering and asset
care knowledge so that they can solve more problems, become more knowledgeable,
make better decisions and your plant runs more reliably!
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