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Mysterious voltage

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New User

Sep 18, 2017, 6:01 PM

Post #1 of 2 (472 views)
post icon Mysterious voltage Sign In

This is about a 1992 Ford E-350 with 7.3 idi diesel.

I have trying to figure why my batteries drain down within 3 or four days when the van isn't used. Using my VOM I checked for current and got a very low milliampere reading. But, here is the mystery: I disconnected all (3) positive leads from the main battery (to check for possible shorts). One lead goes to the starter, one for the auxiliary battery, and the main line to fuses etc. I decided to see if I could read current again. But, with the negative lead of VOM still attached to the negative side of the battery, I brushed the MAIN battery cable and got a voltage reading to flash on screen. Not believing my eyes, I intentionally placed my volt meter + lead onto the disconnected battery cable and the - lead to the battery. I got a reading of 0.22 volts with meter set to read 20 vdc. This should not be possible. I double checked to be sure of settings and that I was not touching leads, as humans do have voltage, thinking it might be me. Still 0.22 vdc. NOT possible I thought.

Where is this phantom voltage coming from???

Hammer Time
Ultimate Carjunky / Moderator
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Sep 18, 2017, 7:37 PM

Post #2 of 2 (454 views)
Re: Mysterious voltage Sign In

It's not even voltage you should be measuring. It's amperage.

With dual batteries it may be tricky to measure parasitic drain. The best place to measure it would probably be interrupting the line to the fuse box.


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