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Parasitic Draw Testing

October 2015  
 
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Rob Thompson's Automotive Technology Education Newsletter

Welcome to my newsletter.

This newsletter is to share teaching ideas for auto tech instructors and to provide informational updates on what is happening in CT education around the country. 

Parasitic Draw Testing Using Voltage Drop


Several years ago at a NACAT session, I learned about testing parasitic draw by measuring the voltage drop across each fuse. For some unknown reason, having sat through the session and even seeing the test in action as part of the session, I didn't start using this method until recently. 

To put the test into practice, I used a vehicle recently donated by our city, a 2000 Olds Bravada. The battery will go dead if left sitting in the lab, so this seemed to be a good candidate for the test.

To begin, I used a DMM to measure the voltage drop across each fuse in the underhood fuse box, shown in Figure 1. All the other fuses read 0.0mV except for one, the TCB fuse, shown in Figure 2

Figure 3  shows a DMM connected in series at the battery negative terminal and negative cable to measure actual current draw. This is for demonstration purposes since the voltage drop method does not require measuring the current flow from the battery.The second DMM is showing the voltage drop across the suspect fuse. The DMM shows a voltage drop of 1.28mV, not a lot but none of the other fuses showed any voltage drop at all.

 

Figure 4 shows the current draw with the fuse removed. 

Using this method is a quick way to narrow down a parasitic draw. My plan is to make or adapt a tool to match up with the openings in the fuse bodies to make testing even faster.

More to come next month.
 
Stay Tuned!

What's going on in auto tech and in education.


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SPY Car Act- Securing Our Cars From Hackers

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Intel Announces Automotive Security Review Board

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Bosch has groundbreaking battery technology for electric vehicles

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10 Automakers Will Make Automatic-Braking Standard

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Roadblocks to Autonomous Driving
Head to my website for PowerPoints, waveform images, and photos that are available for download for instructional use. Recently added are many new mini-lesson PowerPoints, syllabi, and various worksheets.

If you want to use resources shown in this newsletter, links to the lab activities and images can be downloaded and used for instruction from here.
 

Proud member of the North American Council of Automotive Teachers (NACAT).

NACAT is devoted to automotive education and to the teachers and trainers of automotive technology. 


Join us at the NACAT conference at San Jacinto College in Houston, Texas, July 2016.
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