Resistance Across Positive & Negative Cables

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When I measure the resistance (-)COM electrode to negative cable and (+) electrode to positive cable, I get 7 ohms. (Of course, when the two electrodes touch each other, I get 0 ohms and when they
are not touching themselves or anything else, I get infinity ohms.)
However, when I measure the resistance (-)COM electrode to positive cable and (+) electrode to negative cable, I get infinity ohms.
Since the battery is completely disconnected and conductivity knows no direction, what component could allow conductivity in one direction, but not in the other???
Joe

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'Conductivity knows no direction' is not always true. A diode conducts only in one direction, as you probably know. Which makes me suspect your alternator. Disconnect the alternator and check the current draw again.

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When I removed the altenator, the draw dropped to 0.03A, but the I still have "good" conductivity between the positive and negative cables, in both directions, with the battery disconnected.
Is this acceptable?

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You certainly found the problem. Measuring resistance with any kind of electronics (radio, engine management computer, cruise control, ABS controller, clock, etc, etc) connected is practically useless. The main reason is that the ohmmeter uses a very low voltage, at which the circuits are totally out of their normal realm of operation. The detailed explanation will be very boring for those with no interest in electronic circuits... So unless you can assure that all of those devices are disconnected, current draw at the actual battery voltage (and the proper polarity!) is the only meaningful test.

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I found the culprit drawing 3.8A on my 93 Mustang GT...
The 3-wire connector on the top of the alternator was fried as was the component into which it was plugged.
Once I removed/disconnected the alternator, the draw dropped to 30mA.
I have fully charged my battery, spliced on a new connector and installed a new alternator. I hope I am ready to go.
My plan forward is to monitor the condition of my battery each morning and after any long non-stop trips and if I notice a drop in voltage or amperage, try to determine the cause.
Any other suggestions, anyone?
Thanks, again, for all your help!
Joe

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Diodes

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Joe Colella wrote:

Measuring resistance across the cables won't tell you anything. You need to measure current draw with everything turned off and the doors closed. Less than .05A is acceptable. One very common culprit is the voltage regulator. Shorted diodes in the alternator are also common. I recently had a vehicle that the factory radio was causing a 3A draw, and another where the EATC was continually powering the Blend door actuator. Pulling the fuses one by one should narrow down which circuit the draw is on.
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