Voltage Drop Test

  • Xyius
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4 years 3 months ago - 4 years 3 months ago #64363 by Xyius
Xyius created the topic: Voltage Drop Test
Hey Everyone,

In the past I have had people tell me that they do not understand voltage drop testing. So I made a little video explaining the concept (Using a very basic, and intuitive approach).



I am not sure if I am allowed to post links to my YouTube Channel, if not then just delete the thread.

EDIT: Interesting.. The video embed doesn't seem to be working. Here is the link..
Last Edit: 4 years 3 months ago by Xyius.
The following user(s) said Thank You: exceptionalchris

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4 years 3 months ago #64426 by twiggy02919
twiggy02919 replied the topic: Voltage Drop Test
Good job. This should help a,lot of people.

Automotive engineer specializing in sensors.

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4 years 2 months ago #64599 by EricTheCarGuy
EricTheCarGuy replied the topic: Voltage Drop Test
It's totally cool that you post your own videos, in fact, it's encouraged.

I think your explanation is a little off however. Yes, lots of people use the 'pressure' analogy when talking about electricity but I think in this case it would have been better to go at it using Ohm's Law rather than spending so much time on the pressure analogy. A circuit uses ALL of it's voltage in the circuit. So if you start with 12v by the time you reach the end of the circuit you'll have 0v. This is the voltage drop. If you find that you have substantially less than 12v before the load, then you've found your resistance. Of corse you'll loose a little voltage through the circuit but not nearly as much as you would loose passing through the load. After the load in a normal circuit, you will have lost most of your voltage due to ohms law and how the circuit works.

I just wrote an article on this that will be out with the new website. I go into a more detailed explanation there. I also hope to make my own video on this topic at some point.

I appreciate your contribution. Thanks for the post.

Stay dirty

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4 years 2 months ago - 4 years 2 months ago #64607 by Wrench Turner
Wrench Turner replied the topic: Voltage Drop Test
It's important to realize why you are doing a voltage drop test....

A: to check for 'unwanted' resistance.

The unwanted resistance can appear in the following forms:
  • quality of connection
  • material of the conductor
  • thickness of the conductor
  • temperature
  • corrosion
  • physical damage

Learn how to look for and find that bad case of VD. B)

(awesome vid btw)

"Do not catch yourself on fire."
Last Edit: 4 years 2 months ago by Wrench Turner.

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4 years 2 months ago #66412 by moparfan7008
moparfan7008 replied the topic: Voltage Drop Test
realfixesrealfast has a four part video on voltage drop testing that can be useful. In part four, he demonstrates a powerprobe 3.

part 1

part 2

part 3

part 4


here's one I really like though:

the lead he uses on the positive lead of the dvom is a load pro.

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3 years 10 months ago #76848 by bdazsvt03
bdazsvt03 replied the topic: Voltage Drop Test
The best place to learn about anything electrical is by scannerdanner. You can also buy his book. Look him up on YouTube. He is a friend of Eric's also. His book is amazing and so are his tutorials

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3 years 10 months ago #76849 by Raistian77
Raistian77 replied the topic: Voltage Drop Test

bdazsvt03 wrote: The best place to learn about anything electrical is by scannerdanner. You can also buy his book. Look him up on YouTube. He is a friend of Eric's also. His book is amazing and so are his tutorials


Yeah, I love his videos, he does a pretty good job of explaining electrical issues.

Church: No matter how bad things may seem-
Caboose: They could be worse.
Church: Nope. No matter how things may seem they can't be better and they can't be worse. Because thats the way things are and you had better get used to it nancy so quit your bitching

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3 years 10 months ago #77841 by PsychoticMechanic
PsychoticMechanic replied the topic: Voltage Drop Test
Scannerdanner is the guy you want to work besides in a shop for those "please help me i cant for the life of me figure it out situations" when it comes to hardcore drivability and electrical work. Yes I just went way off topic but his videos are very complex if your just a DIY.

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3 years 10 months ago #77872 by Raistian77
Raistian77 replied the topic: Voltage Drop Test
That load pro is pretty slick, I am going to have to check one out.

Church: No matter how bad things may seem-
Caboose: They could be worse.
Church: Nope. No matter how things may seem they can't be better and they can't be worse. Because thats the way things are and you had better get used to it nancy so quit your bitching

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3 years 10 months ago #79598 by juels98
juels98 replied the topic: Voltage Drop Test
I'm still having a hard time understanding Voltage Drop even after watching a bunch of videos.
BTW, I liked this series:

http://www.youtube.com/watch?v=4f-vWFOYmxI

I get the main 2 points:

1. Current has to be flowing
2. At the end of the circuit, all the voltage supplied to it needs to be used up.

However, what I'm having a hard time with is the car circuits are made up of many components each adding it's own load (resistance) right? So how do you make sure the value you're reading on the meter is the correct value? How do you actually go about testing each in the car? What's the general rule? Do you always have one lead on the battery and use the other lead to check the drops? All the examples in the video deal with one load.

Also, I think the name Voltage Drop is kinda misleading. I initially thought it's a test too see how much Voltage "Drops", but it actually is a test to see how much Voltage Remains :) since in theory-- all of it has to drop.

WARNING: I'm no mechanic! I just play one on this forum.

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