Don’t Forget the Basics
Don’t Forget the Basics

Before I begin, I would like to express my respect for technicians. They have a difficult job and many are highly skilled and reliable. However, as an inspector, I have noticed that technicians far too often rely on technology and past experiences rather than the basic fundamentals of diagnostics. The actual problem can be overlooked due to technicians depending on high tech equipment and the multitude of modules that are standard in most of today’s vehicles. Starting with step one – doing an overall check of the vehicle - seems too simplistic and is often bypassed, even though it takes very little time and usually does not require specialized tools or equipment. Therefore, an inspector should never assume the basics have been checked. Although it is not an inspector’s job to diagnose the problem, taking the time to do so can sometimes reveal the actual cause of failure or a potential pending failure. Below, I have chronicled times when this has occurred in my own personal experiences.

  1. The technician claimed a vehicle’s overheating was caused by no coolant flow in the radiator due to a failed water pump impeller very rare. The actual problem was caused by a worn radiator cap that was not pressure tested.
  2. The technician claimed the failure of a front wheel bearing was due to excessive play at the wheel. The wheel was very loose. The C/V axle nut did not appear to be threaded all the way on to the shaft. After asking the technician to tighten the loose nut, the play was eliminated.
  3. When inspecting a diesel with a supposed fan clutch failure and a code of “circuit failure/no communication,” I found the problem to be a severed harness at the connector caused by, none other than the fan itself! The technician never checked the connector!
  4. The technician claimed that no voltage to the alternator was due to failure to the harness. He came to this conclusion because “they see it all the time.” Failure was actually due to a very loose battery cable end at the battery. The technician actually thanked me for discovering the loose cable because he was not looking forward to replacing the harness.
  5. The technician claimed that all TPMS sensors had failed because they all had codes and would not reset. The vehicle was a ¾ ton truck with new tires that required 78 psi in the front and 55 psi at the rear, as stated on the tire placard. All four tires had 45 psi. After inflating the tires to the proper pressure the warning light turned off.
  6. After replacing the left rear folding seat back motor on a van, a technician found that the right side would not raise properly, even though it had been working when he lowered it. Therefore, he claimed it also needed a new motor. The failure was actually caused by the headrest binding on the front seat back because the technician had not removed the headrest before lowering the seat.

Other basic checks that are often overlooked are fluid levels. This is an area that should not be overlooked by the inspector because it can, at times, reveal the cause of failure. Examples of these occurrences are included below.

  1.  The technician claimed failure to the compressor was due to a severe leak. Only light seepage showed under the black light and amber lenses. I had noticed the cooling fan connector was loose and figured he must have checked the power to ground for an electrical issue that was keeping the compressor from engaging. After some questioning, I discovered that he could not get the compressor to operate, but since it was leaking, he felt it should be replaced. I told him I had found that the coolant level in the reservoir and radiator were empty, therefore, that sensor may not allow the compressor to engage. After topping off the coolant, the compressor engaged.
  2. The technician spent two days running tests to diagnose very rough engine vibration and some blow-by on a used replacement motor brought back by the owner after less than 30 days of use. After performing my basic checks, I told him that I had found the problem. The problem turned out to be the oil, which was very much overfilled. He drained ten quarts out of a five-quart system. The vehicle ran smoothly after the pistons were no longer being smashed into the oil. Even though it was the owner, rather than the technician who was responsible for the excess oil, the technician said calling the extended warranty company back was going to be the most embarrassing phone call he would ever have to make!

Checking fluids is a must on all transmission repairs due to possible intermix from ruptured transmission coolers built into radiators. This is a problem some vehicles are notorious for. I make it a habit to look in the oil filler when there is a direct view into the valve cover. Sludge and varnish can be detected at this time. I once came across a vehicle with intermix in the radiator, but also heavy intermix in the engine. After some questioning, I found out the shop knew of the condition but did not report it to the extended warranty company. I suppose being a transmission specialist shop might have had something to do with it!

It is obvious in all these examples that step one was skipped in the diagnostic process. It is for this reason that I feel an inspector should never assume the technician has done the basics.

About the author

Walter Macias


Walter Macias is an independent mechanical inspector in the San Antonio, Texas area. He has 36 years of experience in the automotive industry. He has experience as a business owner, machinist, service manager, and service advisor.

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