Do you remember the first time voltage drop kicked your butt?

Bruce Technician Spring Hill, Tennessee Posted   Latest  

Michael Christopherson's post got me thinking about this. I'm not sure if it was the first time but it's the first time that I remember. It was a Nissan pickup no crank. I remember unplugging the starter solenoid and checking for power with a DVOM. Hooked it up and turned the key to crank, meter showed 12 volts so I sold a starter. Of course it didn't fix it. So I replaced the relay and it started. That was about 18 years ago. 

Unfortunately, that didn't set me on the path to figure all this stuff out. I didn't go to school for auto repair and my "mentor", my Dad, always said there was no money in that part of the business. It wasn't until late 2016 that I started really trying to learn electrical and diag. Since then I have taken several ATG and SMP classes, Super Saturday last year, Vision and ATE this year. Going back to Super Saturday this year. Wish I had started down this road a long time ago. 

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Dustin Owner/Technician
Lakeland, Florida
Dustin
 

Yes I do, it was an older gm, 3.8....bad body ground that took me way to long to find.

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Scott Manager
Claremont, California
Scott
 

About ~30yrs ago I remember an early 80’s GM towed in for a no crank. I started with an under hood inspection look and ‘feel’ and this is where I learned! I’m sure that there are many here that remember the small flat braided copper ground strap that ran from the firewall to the intake or the back of a cyl head. Well, as I was probing (pre labscope days) for some reason I reached in to touch

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Geoff Diagnostician
Lahaina, Hawaii
Geoff
 

Yup. Wiper motor on an 80's Chevy pickup. When the reman didn't work, I just ordered another one. When that one didn't work I gave it some more thought. I found that the fuse was dirty. Didn't take long, but I felt stupid for the rest of the day.

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John Instructor
Beaver, Pennsylvania
John
 

1977 Ford Maverick Grabber. It would shut down on the road at random times. When it quit it lost spark. The typical routine back then was to connect a test light from ground to the coil negative and watch the ignition command. Those Duraspark systems turned the coil on, and only turned it off to fire the spark plug. The lamp would go out when spark was lost and the first few times I experienced

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Walter Technician
Sarasota, Florida
Walter
 

In all actuality voltage drop is what keeps guy's like us in demand! I had this one last week, 96 VW Golf running rough with check engine light. The codes P0501, P1237,P0125,P0300 and P0301. It already had No.1 injector and tune up components done to it so I hooked up the scope on injector's 1 & 4 and current on injector fuse, Immediately I knew I had a connection or ECM issue. I inspected

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Walter Technician
Sarasota, Florida
Walter
 

The scope capture of 1 & 4 was not included in post at this time.

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Martin Instructor
Burnaby, British Columbia
Martin
   

Absolutely! I recall the details with full clarity like it was just yesterday. I always use this particular example and openly share my "butt kicking" experience with my students, when discussing the value of performing voltage drop testing. In 1975, I worked in an Esso Service Station in Vancouver at the time and got "married" to a no start diagnosis for three days that kicked my butt good and

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Scott Instructor
Tulsa, Oklahoma
Scott
 

Do I remember the first one I got fooled by? And how... the first 'serious' (expensive) voltage drop problem that kicked my butt was on an early 80's GM cruise control. The activation signal at the ECM seemed fine (using my new neon test light I got off the tool truck) and I didn't really see much of a discoloration (the typical dull brightness of a weak signal) from the test light bulb. When I

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