Voltage issue

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Aug 13, 2015 | 09:25 AM

tainplum

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Voltage issue

I searched the forum and couldn't find anything. Here is what it is doing when I start the car cold the voltage is a little over 13v on the gauge as the car is driven a couple miles it drops a little below 13v and stays there no matter the rpms.

Aug 13, 2015 | 06:58 PM

merphie

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I have a similar problem but mine drops when idle.

Aug 13, 2015 | 08:05 PM

hrcslam

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Voltage issue

First you need to verify the dash gauge is accurate.

Aug 14, 2015 | 02:11 AM

wssix99

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So, what is the issue?

Aug 14, 2015 | 03:42 PM

McGinnis

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Alternators loose efficiency as they warm up slightly. At cold start it might be closer to 15v and after a couple minutes it will be about 13.5v with the engine on. Also remember the dash gauge is not very accurate, a voltmeter at the battery is the only way to know for sure. As long as it doesn't drop under 13 volts at idle with radiator fans and dash blower fan running it's probably fine. With the engine off the battery will read around 12.8ish volts.

Aug 15, 2015 | 11:53 AM

merphie

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My battery always reads about 11 -12 volts and I don't have a huge amp draw so I just figured the gauge was inaccurate.

Aug 16, 2015 | 08:25 AM

tainplum

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Ill put a volt meter across the battery to see what it reads at first start and after a drive. Was just curious if it was an indication of my alternator going bad.

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Aug 17, 2015 | 07:15 AM

wssix99

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Quote:

Originally Posted by tainplum

Was just curious if it was an indication of my alternator going bad.

The gauge on the dash is not very precise. If you want a precise measurement of system voltage, you can plug a scanning system in to the OBDII port, but they cost $$$. You can also measure voltage across your battery with the car running if you want to see what its like at idle. (Measuring voltage across your battery can probably be done while you are moving - but you'll need to find the right volunteer!)

Your alternator will throttle back output after the car has warmed up and it senses that it has charged your battery back up. I would expect that might be what you are seeing.