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voltmeter

This is a discussion on voltmeter within the General Help forums, part of the LSx Technical Help Section category; What should the voltmeter read on our cars? My batteries seem to be running dry every year and my stereo ...

  1. #1
    Junior Member Valor X's Avatar
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    1999 Pontiac Trans Am

    voltmeter

    What should the voltmeter read on our cars?
    My batteries seem to be running dry every year and my stereo stops working unless I charge the battery.
    My voltmeter reads right at the begging of the yellow line which appears to be 12v when the key is in the ignition
    On a cold start it goes up to about 15v and will stay there throughout the drives.
    Is this normal? Or might I have a bad alternator?

  2. #2
    Junior Member Valor X's Avatar
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    bright red
    1999 Pontiac Trans Am

    EDIT**
    It takes just about 4 miles of driving before it drops down to about 14v (and I had headlights, foglights, and heater on)
    Is this too high?

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    Senior Member Too Fast's Avatar
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    2000 WS6 6spd Hooker LT

    The volt gauge is not perfect, so I would get the charging system checked. The alternator is controlled by the PC, it turns the alt on and off. If your car really is running over 15v, that will diminish battery life. Normal battery charging system voltage should be between 13.5-14.5. Cold weather maybe up by .5 max, warm weather should be more near 14. Make sure the grounds are good, if the PC isn't getting a good signal it can affect it's ability to control the alt.

    What do you mean about your batteries running dry? I assume you meant they can't hold a charge anymore? Have you had to replace the battery every year? How long can you run the stereo before the battery goes dead, is your stereo stock or do you have an amp powering subs or more. If you usually run your stereo with a high draw on the battery (like washing/waxing/detailing the car, or at a car show) get a small charger to assist the battery during those times. Multiple drain situations on a conventional lead acid battery severely shorten its' life. You might consider a different type of battery (AGM, deep cycle, etc.).

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    Senior Member JayTA98's Avatar
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    1998 Trans Am

    Mine had always been around 14.1 at crank and it stays around 13.8 while driving until the fans turn on. Once the fans are running the voltage drops to 12.8-13.1 at idle during daytime. At night time with headlights on, etc at idle it can drop to 11.9v. I had this issue since i got the car 5 years ago. I had replaced alternators, all big 3 power cables and battery but the issue remains. I get the same reading with a second voltmeter that i have installed and even with a voltmeter connected at the battery. When the car is driving around the voltage is constant 13.5-13.7.

    The car had never stalled, the headlights has never dim, etc. I'm bot sure if is a PCM issue or just normal for my car so i just left it alone. All other vehicles I owned the voltage never dropped under 13.5v

  5. #5
    Member initechpeter's Avatar
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    2002 Trans Am WS6 - Red
    2013 Chevy Traverse LTZ

    Quote Originally Posted by JayTA98 View Post
    Mine had always been around 14.1 at crank and it stays around 13.8 while driving until the fans turn on. Once the fans are running the voltage drops to 12.8-13.1 at idle during daytime. At night time with headlights on, etc at idle it can drop to 11.9v. I had this issue since i got the car 5 years ago. I had replaced alternators, all big 3 power cables and battery but the issue remains. I get the same reading with a second voltmeter that i have installed and even with a voltmeter connected at the battery. When the car is driving around the voltage is constant 13.5-13.7.

    The car had never stalled, the headlights has never dim, etc. I'm bot sure if is a PCM issue or just normal for my car so i just left it alone. All other vehicles I owned the voltage never dropped under 13.5v
    This is the same way mine is with the voltage. It will be high for most of the day then i drops down to about 11.

  6. #6
    Junior Member Valor X's Avatar
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    1999 Pontiac Trans Am

    I have the stock stereo and I don't use it when the car is off to wash the car
    Last year I had to replace my battery when some electronics such as the stereo were not working.
    Now the same exact symptoms are back and I'm surprised since I invested in a redtop optima battery
    My concern is that my system is not properly charging the battery which is probably the case that you're mentioning optimal battery recharge is at 13.5v when I'm always close to 15v
    But it could possibly be the cold weather as well why I'm getting these symptoms in the winter... but I live down in Texas so go figure

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