Working Backwards

With the ever-increasing use of electrical and electronic systems in almost all vehicle areas, many automotive and heavy vehicle training schools are shifting their focus to cover a more analytical approach to diagnosis. Critical thinking and deductive reasoning are replacing--at least in part--rote practice of hands-on tasks. This is primarily because the process of making electrical system repairs is often quite different than that for mechanical repairs.

In a recent Manager’s Digest article at, Dan Sullivan notes that the ways in which electrical system and mechanical problems are found and repaired is usually inverted. With mechanical concerns, the diagnosis often starts with a fairly obvious visual clue: an air hose blew, an oil or coolant leak is present, a cylinder head cracked, etc. It may take some additional digging to find a root cause, but at least the technician has a good starting point.

With mechanical failures, "diagnosis is generally about 10 percent of the job and repair is about 90 percent. The reverse is generally true of electrical system problems."1

Thus, good electrical technicians must have strong critical thinking and creative problem-solving skills. Because of the nature of electrical problems, it is often difficult to "see" what is happening in a circuit. Rather than a bottom-up approach, such as using visual and physical clues to work toward locating the root cause of a concern, the electrical technician must often use the results of tests and work backwards (top-down) to determine where test results do not match expectations.

I often get second looks when I use the phrase "critical thinking skills," given that "skills" are most often associated with psychomotor activities. Certainly there is a knowledge element to critical thinking--technicians must learn and/or be trained in the detailed operation of electrical systems. But there is also a "skill" to taking that knowledge, organizing diagnostic steps in a logical sequence, and formulating a diagnostic plan.

Learning to navigate service publications and electrical schematics is also important in developing critical thinking for electrical diagnosis. Service publications, in particular, do not always organize their diagnostic sections in a logical manner. Possible causes listed for an error code, for example, are not always organized from the least intrusive (to test) to the most intrusive. The educated technician can formulate a more logical diagnostic plan that reduces unnecessary testing time.

Fleet and service managers must also realize that building good electrical technicians is a stepped approach. Technicians must progress from the basic, universally-applicable electrical knowledge to more advanced critical thinking and troubleshooting skills, followed by the necessary product-specific technical training.

Expectations of the technician when he returns from training can often be too high, at least initially. This is partially fueled by the "reverse" nature of electrical work Sullivan highlighted. When the technician takes time to read a manual or study schematics as part of a logical approach to electrical troubleshooting, it can be perceived as "inactivity" by the service manager and others. "This pressure," states Sullivan, "rushes too many mechanics through electrical diagnoses."2

Yet the unnecessary replacing of good parts, which often occurs during "trial and error" diagnosis, can delay the discovery of the actual root cause even further. Allowing a technician the time to "get his feet wet" while taking the correct, logical approach to electrical diagnosis will pay the fleet manager back in the long run.

1, 2 Sullivan, Dan. "Manager’s Digest" at, Feb. 1, 2009