Basic Troubleshooting Questions

One of the most important skills a Technician has is the ability to troubleshoot and find problem areas in a system, no matter what kind of system that is. It could be electrical, mechanical, hydraulic, or otherwise. All you need is the basics of a system to figure out what could be the cause of a problem, and asking yourself, or the person who needs help, some simple questions, to lead you to a problem area.

Prior Occurrence

If a device has been known to fail in the past, especially in a particular way, and the conditions leading to this failure hasn’t changed, check this first. If this is a computer-controlled system, like a car, it should have a failure log so that when problems occur they can be stored and referenced with date, time, and even environmental conditions. This helps the technician look in certain areas of the system.

EXAMPLE: Your car keeps overheating. Last time it was low coolant in radiator.

WHAT TO DO: Check coolant level to see if it’s low. Fill up and let run with cardboard underneath where the coolant tubes would be. Notice where the drips are and see if you can tell where they are coming from.

Recent Changes or Modifications

Sometimes after a system has been fixed, after changes or alterations of that system, check that first. Those problems may be linked to those changes.

EXAMPLE: The car’s right tire is losing air after replacing all the tires at the mechanic.

WHAT TO DO: Spray the tire with soapy water to see where the air is leaking out of. It could not be sealing correctly on the rim, or a valve stem is bad. Take back to mechanic.

Function / Non-Function

If a system is not functioning correctly in one mode of operation, look for what it is doing correctly in another mode of operation. Isolate between the subsystems and look towards what is not common between them.

EXAMPLE: Car trailer lights are working on both sides, but the right blinker is not.

WHAT TO DO: Look at schematic and notice that the green wire is the one that controls the blinker on right side. It could be that the blinker bulb is out. You can replace the bulb and see if that fixes it. If not, it could be a break in that wire somewhere, or the signal from the car is not working. Use a multi-meter to check continuity in the green wire, or voltage at the bulb when the blinker is activated. Also, you could check voltage at the connector coming from the car to determine if the problems lies at the beginning of the circuit.


For what you know about a system, list possible types of failures that may cause a problem to occur. First, use your senses that God gave you: sight, smell, sound, taste, and touch, and then start eliminating possibilities using this information. When I used to work for a company fixing mail room sorters and openers, I could hear sounds from across a room and know something wasn’t right, which led to either grinding bearings or motors failing.

EXAMPLE: Driving along you hear a bang under the car and something hit underneath. Moments later the car is overheating and struggling to keep moving. You manage to pull the car over into a parking lot.

WHAT TO DO: You see that the coolant gauge is hot, and lights do not work. As soon as you get out you notice a smell of antifreeze in the air and can hear a faint whistle. You carefully open the hood and see that vapor is streaming out the large hose on top of the radiator. But you wonder why the lights don’t work. You brainstorm to see what common points are between the coolant and the alternator that creates electricity for the vehicle. You continue to check to look for other issues and notice that the main belt is laying on the engine. You try to put it back on and notice that the idler pulley is completely gone.

In the future, I will post how to use specific troubleshooting techniques to isolate areas of component failure. If you think I missed anything in this post, feel free to comment and add your own. I love to learn new things from my readers.

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