Voltage drop is a better way to measure resistance. Worst case scenario would be a battery cable with just one strand left intact.
Turn VOM to Ohms and put the red lead on the + battery cable end and the black lead on the other end of the cable to the starter. You read zero Ohms resistance. Now, with the same connection, turn your VOM to Volts. It should read zero volts because there is no potential across the battery cable.
Now turn the key and that one strand is high resistance and now you will read almost battery voltage. You now have potential across that wire. The single strand is high reistance, but there is some voltage going across it, but the rest of what you are reading is the potential.
I'm explaining this poorly....
Let me try the WWW. This guy starts out by saying,
I am an Electron Wrangler. While I'm not allowed to wear a cowboy outfit, my employer pays me to ensure that various electrons go exactly where intended and nowhere else.
so you can trust him.
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You may suddenly find yourself consumed with the urge to hurt me. Your Jeep's starter barely turns, and I'm delving into the seemingly unimportant details of a voltmeter. Before proceeding (I'm talking about reading further, not hurting me) it is vitally important to understand that there is no pressure difference between the meter leads when they are connected, and thus 0.000 volts is displayed. That sounds pretty basic, but what does that have to do with anything?[/FONT]
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If I haven't lost you yet, consider this next step. Instead of the meter leads connected directly to each other, what would happen if they were joined by a "Perfect" conductor? (There is no such thing as a "Perfect" conductor, but "Pretty Darn Good" is well within our grasp.) With the meter leads joined by a "Perfect" conductor, it is the same as if the leads were directly connected:[/FONT]
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That piece of wire shown above happened to be completely isolated from anything else but the meter. Consider if that "Perfect" conductor was part of a circuit in motion. Even if bazillions of electrons were zipping past (Very high pressure or voltage) there would be no pressure differential between the meter leads. This is the very crux of this simple troubleshooting technique. This allows us to verify that any circuit element is allowing electrons through with no unwanted resistance. In this TooMuchFreeTimeVision(tm) image, the happy blue electrons are zipping past as part of a completed circuit. As with the piece of wire shown above, the meter is indicating 0.000 VDC:[/FONT]
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Now let's place a restriction in the previously "Perfect" conductor. For the moment, consider it an unwanted restriction like a loose crimp or multiple broken strands. The restriction may not be as abrupt but is enough to cause a difference in pressure along the conductor. If too many electrons try to pass through, they will bunch up on the upstream side of the restriction. Remember this conductor is part of a circuit in motion, with the electrons traveling in a loop and performing useful work, such as powering a light. Even though we no longer have a "Perfect" conductor, we do have a theoretically eternal voltage source of stable output pushing the electrons. (Thanks, Craig!) Notice how the meter is not reading zero any more:[/FONT]
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The voltage displayed is directly proportional to the amount of the restriction. Pretty cool, huh? With a simple meter hookup, a circuit under load can be easily tested for any unwanted restriction, or voltage drop. This is called a voltage drop test and is amazingly simple in use. It can be a bit difficult to grasp initially, so reread this section until it makes sense. Then sit on your hands, because you'll want to slap yourself once you realize how simple it is. The closer the voltage reading is to zero, the better the conductor is. Don't forget the all-important fact that this only works on a circuit in motion.[/FONT]
He explains it better than I do.