What motivates you to learn?

Feb. 1, 2018
I wasn’t angry because I had lost the technician competition. I was angry at myself because I had tried a testing method I was sure I understood and failed. (OK, maybe I was also a little angry that I lost.)

The last shop I worked for full-time was a national chain that specialized in reconditioning used cars for sale. Internally, we had two distinct “teams;” one made up of techs who inspected and repaired the incoming stock and the other of techs who took care of our retail and warranty customers. I was on the latter.  

The company, at that time, held annual contests for its technicians. Techs competed against one another first on a state level with the winners going head to head in a regional competition. Those winners, in turn, competed for top honors at a national event. I participated in the contest that first year and was successful in earning a slot at that national contest. And I was very optimistic about my chances at winning there, too. 

Relying on skills learned in days past will only take you so far when dealing with more modern systems.

I blew away the written part of the contest, and aced every skill station I was assigned. It was all going to come down to the hands-on troubleshooting challenge. The judges had bugged several GM trucks in order to generate a DTC and turn on the vehicle’s MIL lamp. We would be judged on our speed in coming to a successful diagnostic solution.  

Watching it slip away 
I don’t recall the DTC, a P0101 (MAF sensor circuit range/performance problem) I think. What I do remember is that it was more than likely a circuit issue and I should be able to nail it down pretty quick using a technique I had recently read about. Something called “voltage drop” testing. 

At first, I did what many still do today. I unplugged the connector and measured power to the sensor. At the time, I didn’t realize or understand that I was only measuring OCV (Open Circuit Voltage) and wasn’t really testing the circuit’s actual ability to provide full voltage in the working circuit. I then moved my leads to the ground side with the connector plugged back in. The meter was trying to tell me that I had located a problem on the ground path, but I wasn’t seeing it. My test procedure was correct but I didn’t understand the concept of how voltage drop worked in a “live” circuit. All I could remember thinking was, “How can I be measuring voltage when my leads are attached to a ground point on both ends?” I questioned my lead placement, my interpretation of the wiring diagram and even began wondering if the meter I had been provided with was working properly. My judges could see my building frustration and tried to provide me with little clues, to no avail. I was lost – pure and simple. 

And it cost me the competition. And that ticked me off. 

I wasn’t angry because I lost. I was angry at myself because I had tried a testing method I was sure I understood and failed. (OK, maybe I was also a little angry that I lost.) 

What are you going to do now? 
That anger fueled a strong desire to really learn what I thought I had already learned. I went back to the source I had first found and reread everything I could find on voltage drop testing. Then I went out to the shop and built a simple circuit with a battery, some wire and a couple of light bulbs.  

First, I wired just one bulb to the battery. Then I took my meter and measured voltage on the positive side with the bulb lit, and then moved my meter lead to the ground side. Keep in mind that I’m using the positive meter lead to take the measurements while leaving my meter’s negative lead grounded to the negative battery terminal.  

I read near battery voltage on the first measurement but this was no longer OCV that I was reading. This was now a loaded circuit and the voltage first had to pass through any other sources of resistance in that circuit before it made it to the bulb. And that’s when the first “bulb” went off in my head! The reading was slightly less at the bulb connection because of the resistances encountered along the way; the point of connection at the battery and the point of connection between the wire I was using and the existing bit of wire from the bulb’s original harness I had the bulb plugged into. 

The ground side read a few tenths of a volt and the second “bulb” went off. The 12 volts (and change) that I had measured earlier had been consumed by the bulb, the largest source of resistance in my circuit. The few tenths remaining were there to overcome the remaining resistances in the circuit as it returned to the battery; the bulb-to-wire connection and the wire-to-battery negative connection, as well as the wire itself. 

Ok, OK – I think we’re starting to understand now. But the “bug” the judges had used in the contest was the addition of a small resistor on the ground side of the MAF sensor. I had to duplicate that “bug” and see what would happen to the meter readings. 

Adding a thief 
I wired a second bulb to my test circuit, placing it in series on the first bulb’s ground side. When I bridged the connection back to the battery, it was easy to see the effects of the added resistance. The second bulb glowed dimly but the first bulb was nearly non-existent. Time to take the measurements again. 

I didn’t expect to see a change on the positive side of the first bulb and I didn’t. On to the second measurement on the ground side of bulb #1 – and I got a reading of over 7 volts. You would think that I would know by now why I was reading voltage but in my mind, I was still thinking like I had at the contest and was trying to understand how I could measure voltage on a ground! It was an internal block, caused by all of my preconceived notions and experiences on how a ground should act. 

It may not look like a fancy learning aid but it was all I needed to finally make sense of voltage drops.

I then moved my meter lead down to the “positive” side of the second bulb. I measured the same 7 volts here. Perhaps it was the placement of the meter lead in relation to the load that finally started the third, and final, “bulb” to go off in my head. I had read 12 volts and change on the positive side of bulb #1 and understood that was the bulb’s source voltage. Now, I only had 7 volts source voltage. What happened to the other 5 volts? 

Of course! It was consumed by the first bulb! Then the electrical rule that all source voltage will be consumed proportionately by all the resistances in the circuit began to resonate in my mind. Here it was, in living proof! Moving my lead to the ground side of bulb #2, I measured the same few tenths that I had in my initial experiment. As the rule said, the (now) two major sources of resistance in the circuit consumed the majority of the source voltage I started with. 

So when I measured 7 volts on the ground side of the first bulb, the meter was telling me that there had to be a source of resistance yet to come. The concept of using voltage drop as a testing method finally made sense! 

And it was so simple! 

I admit, I am not fluent in electrical testing and still have to stop and think about my meter readings from time to time. But I also know that this illuminating moment changed my entire outlook on how I approach electrical issues and I’ve solved many more of them, and solved them faster, than I would have without this testing method in my arsenal. 

The true moral of the story 
My objective for writing this month’s article was not to share the story of how I lost a competition, or to teach you voltage drop testing. I wanted to challenge you to ask yourself, “What does it take before I’m willing to invest the time to learn?” 

It is easy to become complacent. If we can make a living and support our families on the skill sets we already have, why train on new systems or processes? And it is an unfortunate, but true, reality that way too many of us are that complacent. 

I sometimes still have to take a moment to interpret my meter, but I’m more comfortable with it now than I was at the competition!

I invested the time and energy to learn voltage drop testing because I was angry with myself for thinking I knew something I really didn’t. Ego was definitely involved. But that investment in time and action has paid off in more ways than one. Becoming more proficient absolutely increased my earning potential and the surety of my diagnosis prevented me from wasting valuable time or making an incorrect repair that would ultimately result in a comeback. 

And that, my friends, is what should have motivated me to learn – the desire to grow and maintain my professional skill sets in an ever-increasingly complex field. I hope that’s what motivates you.

About the Author

Pete Meier | Creative Director, Technical | Vehicle Repair Group

Pete Meier is the former creative director, technical, for the Vehicle Repair Group with Endeavor Business Media. He is an ASE certified Master Technician with over 35 years of practical experience as a technician and educator, covering a wide variety of makes and models. He began writing for Motor Age as a contributor in 2006 and joined the magazine full-time as technical editor in 2010. Pete grew the Motor Age YouTube channel to more than 100,000 subscribers by delivering essential training videos for technicians at all levels. 

Connect with Pete on LinkedIn.

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