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Old 08-01-2019, 06:27 PM   #26
Cougar4
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Member#: 53443
Join Date: Jan 2004
Location: Anchorage, AK
Vehicle:
2001 LL Bean Outback
Winestone

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Whenever a bad ground is suspected to be the cause of a problem, running jumper wire from the negative battery post to the suspected bad ground point is a simple and quick way to verify that a bad ground is or isn't the cause of the issue.
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Old 08-02-2019, 09:20 AM   #27
TeeLee
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Member#: 504348
Join Date: Jul 2019
Chapter/Region: MWSOC
Location: Houghton, Michigan
Vehicle:
2004 Forester
blue

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I first pulled the alternator plug, and applied 12V to the black and white wire, and the charge light came on, so I knew the light was functioning properly.
I had an old analog (dial) multi meter, and I checked continuity between the alt. case and the negative battery post, but of course it showed there was some.
I have heard about using voltage drop to determine resistance in a circuit, but I was not sure how that procedure would be applied to find out how poor the contact was between the alternator case and ground.
Luckily, I had a good used alternator to put in as a test. But as I saw, just bolting in a known good alternator did not solve the problem.
I suspect some people may have installed a new alternator, but because the mounting bracket surfaces and mounting bolt faces are corroded that even a new alternator may not get a good ground.
This is a very poor design, there really should be a separate ground strap from the alternator case to ground.
I had replaced my alternator belt a few days before, and I suspect even moving the belt adjustment could cause the case to lose ground contact on an old corroded car.
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Old 08-18-2019, 08:15 AM   #28
fox252
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Join Date: Aug 2019
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Quote:
Originally Posted by Cougar4 View Post
Whenever a bad ground is suspected to be the cause of a problem, running jumper wire from the negative battery post to the suspected bad ground point is a simple and quick way to verify that a bad ground is or isn't the cause of the issue.
Thanks, had an issue years back with a ground wire and should have thought to do this.
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