My voltmeter goes from 14 to 10 when applying brakes. What causes this?

1995 CHEVROLET SILVERADO
83,700 MILES
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CONFEDSURG
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When applying brakes, the voltmeter goes from 14 to 10 gradually. There is no indication of stalling or other problem.
Feb 12, 2012 at 5:34 PM
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RASMATAZ
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Check belt tension if okay-Have the alternator load tested-start here
Feb 12, 2012 at 5:47 PM
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SATURNTECH9
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So does it only do it while stepping on the brake no other time?Do you have a multimeter to do some testing?
Feb 12, 2012 at 5:48 PM
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CONFEDSURG
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Yes, it only happens when stepping on the brake, no other time. I do not have a multimeter.
Feb 12, 2012 at 6:41 PM
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JACOBANDNICKOLAS
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It sounds like there may be a short in the brake light wiring. Usually, if there is a problem with a loose belt or weak alt, the problem will not be limited to only the brake lights.
Feb 12, 2012 at 9:14 PM
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SATURNTECH9
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You will need a multimeter to check grounds etc.I would make sure the brake lights have a good ground.Also that the alternator case has a good ground.
Feb 13, 2012 at 2:01 AM