# Voltage problem..? 1998 Mustang GT

**URL:** <https://community.cartalk.com/t/voltage-problem-1998-mustang-gt/45960>\
**Category:** Maintenance/Repairs\
**Tags:** mustang, ford\
**Created:** [March 12, 2010, 4:49pm UTC](https://community.cartalk.com/t/voltage-problem-1998-mustang-gt/45960 "2010-03-12T16:49:53Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![ditchdoctor](https://avatars.discourse-cdn.com/v4/letter/d/e9c0ed/32.png) [@ditchdoctor](https://community.cartalk.com/u/ditchdoctor)\
**Post date:** [March 12, 2010, 4:49pm UTC](https://community.cartalk.com/t/voltage-problem-1998-mustang-gt/45960/1 "2010-03-12T16:49:53Z")

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When I accelerate at normal speed my voltage meter drops slightly. But when I “unleash it” and take off it really drops resulting in my battery light coming on also. Once I get up to speed in both scenarios it goes back to a norm. I have replaced the battery,belt, and tensioner(per past advice,thank you)but why would this still be happening? Oh and I checked the alternator, told it was ok…? Is this normal?

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**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\
**Post date:** [March 12, 2010, 4:52pm UTC](https://community.cartalk.com/t/voltage-problem-1998-mustang-gt/45960/2 "2010-03-12T16:52:42Z")

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How does the voltmeter act if you just slowly rev up the engine in neutral? Does the car have to be in motion for this to happen?

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**Author:** ![ditchdoctor](https://avatars.discourse-cdn.com/v4/letter/d/e9c0ed/32.png) [@ditchdoctor](https://community.cartalk.com/u/ditchdoctor)\
**Post date:** [March 12, 2010, 4:55pm UTC](https://community.cartalk.com/t/voltage-problem-1998-mustang-gt/45960/3 "2010-03-12T16:55:37Z")

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No the car doesn’t need to be in motion to drop the voltage. It can happen with it sitting still, and mashing the accelerator pedal hard.

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**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\
**Post date:** [March 12, 2010, 5:17pm UTC](https://community.cartalk.com/t/voltage-problem-1998-mustang-gt/45960/4 "2010-03-12T17:17:39Z")

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Did the test involve revving the engine while observing the test voltage? Probably not. I volt for an alternator with worn out brushes.

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**Author:** ![tardis](https://avatars.discourse-cdn.com/v4/letter/t/f0a364/32.png) [@tardis](https://community.cartalk.com/u/tardis)\
**Post date:** [March 12, 2010, 5:32pm UTC](https://community.cartalk.com/t/voltage-problem-1998-mustang-gt/45960/5 "2010-03-12T17:32:52Z")

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I second that vote (or volt). The brushes are flying away from the slip-rings as the rotation speed increases.

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**Author:** ![ditchdoctor](https://avatars.discourse-cdn.com/v4/letter/d/e9c0ed/32.png) [@ditchdoctor](https://community.cartalk.com/u/ditchdoctor)\
**Post date:** [March 12, 2010, 5:34pm UTC](https://community.cartalk.com/t/voltage-problem-1998-mustang-gt/45960/6 "2010-03-12T17:34:59Z")

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you’re right I didn’t but I will. Thanks. I’ll let you know how it goes!

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**Author:** ![ditchdoctor](https://avatars.discourse-cdn.com/v4/letter/d/e9c0ed/32.png) [@ditchdoctor](https://community.cartalk.com/u/ditchdoctor)\
**Post date:** [March 12, 2010, 7:22pm UTC](https://community.cartalk.com/t/voltage-problem-1998-mustang-gt/45960/7 "2010-03-12T19:22:48Z")

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That was the problem. Checked it under load at my local parts store and it confirmed I need a new alternator. Thanks “hellokit” and “tardis”!