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Thread: Alternator Charging Number At Idle

  1. #1
    Still Wrenchin'! friskyfrankie's Avatar
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    Default Alternator Charging Number At Idle

    My friend has a '96 CV. Today I checked his battery voltage and with the key off was 11.65 - too low. At idle it was reading about 13.6 which to me is a tad low. I'd like to see a reading just north of 14. It is a 130 amp alternator. The A/C was on so I would think it should have been even higher. The alternator is at least 8-10 years old. My suggestion is to clean the battery terminals and then take new readings. If they are the same, change both alternator and battery. His theory is since the car starts so fast, leave everything alone. He also thinks I'm losing it in my old age (a separate issue!). What do you guys think??

    P.S. Next test is to check the voltage from the alternator's charging post and case. Then I'll see how it matches up to the reading at the battery posts to see if there is a significant voltage drop. Hopefully, the battery is the only week link causing the shitty alternator numbers.
    Last edited by friskyfrankie; 01-05-2022 at 05:07 PM.

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    take it to a parts store and have them check all 3. Starter, alternator and battery. Simple, quick and wont waste money.
    1987 CV LX 5.0

  3. #3
    Still Wrenchin'! friskyfrankie's Avatar
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    Quote Originally Posted by mcb82gt View Post
    take it to a parts store and have them check all 3. Starter, alternator and battery. Simple, quick and wont waste money.
    Not a bad idea. I do have enough diagnostic tools here so really wanted opinions on the current numbers and any testing suggestions I didn't think of.

  4. #4
    Beater gonna beat sly's Avatar
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    13.6 is fine for idle. The battery may have a weak cell as the 11.6 reading is in that ballpark for 5 strong cells and one weak one. If the battery has a weak cell and the alternator is at full tilt trying to charge that, it will bring the voltage down a little. I wouldn't worry about that alt as much as the battery or the terminals. Cleaning may help.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
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    ... and it should all work like magic and unicorns and stuff.
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  5. #5
    Still Wrenchin'! friskyfrankie's Avatar
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    Quote Originally Posted by sly View Post
    13.6 is fine for idle. The battery may have a weak cell as the 11.6 reading is in that ballpark for 5 strong cells and one weak one. If the battery has a weak cell and the alternator is at full tilt trying to charge that, it will bring the voltage down a little. I wouldn't worry about that alt as much as the battery or the terminals. Cleaning may help.
    Going to clean the posts and terminal ends soon. Always got to do the easy stuff first! Besides, it's easier and cheaper to replace the battery, if needed, than the alternator. I forgot these cars don't idle as high as say, the P71's sp the numbers may seem a little lower.

  6. #6
    I'm an air-conditioned gypsy gadget73's Avatar
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    agree, seems entirely normal for the alternator, but the battery sounds low.

    Either that or your meter is full of lies. How old is the battery / how good is the meter?

    86 Lincoln Town Car (Galactica).
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    Is it sealed or can you get to the cells? A cheap battey float type tester could easily help.
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    Donating Member massacre's Avatar
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    I like to see over 14v when charging
    ..

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    Quote Originally Posted by massacre View Post
    I like to see over 14v when charging
    That's what I'd like to see.

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    Still Wrenchin'! friskyfrankie's Avatar
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    Quote Originally Posted by jaywish View Post
    Is it sealed or can you get to the cells? A cheap battey float type tester could easily help.
    Not sure I have a float tester - will have to look. Yes, I can get to the cells!

  11. #11
    Still Wrenchin'! friskyfrankie's Avatar
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    Quote Originally Posted by gadget73 View Post
    agree, seems entirely normal for the alternator, but the battery sounds low.

    Either that or your meter is full of lies. How old is the battery / how good is the meter?
    Battery is a little over 3 years old (or so I am told). Will double check with another meter. Never hurts to double check one's work as I have witnessed fault meters before!

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    Beater gonna beat sly's Avatar
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    Have someone crank it while you hold the meter on the battery. If it drops below 11V during cranking... weak cell.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  13. #13
    Still Wrenchin'! friskyfrankie's Avatar
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    Quote Originally Posted by sly View Post
    Have someone crank it while you hold the meter on the battery. If it drops below 11V during cranking... weak cell.
    Yeah something tells me there is a new battery going to happen in the near future! Probably a Motorcraft 850. Current one is a Bosch and a little over 3 years old. When I first started "wrenching" (dinosaurs still roamed the Earth), batteries lasted 8-10 years and that was in NY with hot summers and cold winters. Now they seem designed to fail "quickly" so there is a constant replacement cycle.

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    Beater gonna beat sly's Avatar
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    Yeah... batteries are really hit or miss from any manufacturer now. Sometimes you get 8 years from a walmart battery, sometimes 6 months and everything in between.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

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    Quote Originally Posted by friskyfrankie View Post
    Now they seem designed to fail "quickly" so there is a constant replacement cycle.
    Seems the same with wiper blades. They used to last for years and years. Now I seem to change them every 6 months, and i dont buy cheap ones.
    1987 CV LX 5.0

  16. #16
    Still Wrenchin'! friskyfrankie's Avatar
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    Quote Originally Posted by mcb82gt View Post
    Seems the same with wiper blades. They used to last for years and years. Now I seem to change them every 6 months, and i dont buy cheap ones.
    I've had luck with Bosch but perhaps there are others that work as well. Several years ago, Walmart sold wipers from Pylon. Only like $2 each and lasted for years.

  17. #17
    Beater gonna beat sly's Avatar
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    rain-x, michelin, and bosch seem to have the best, but they're all spendy.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  18. #18
    I'm an air-conditioned gypsy gadget73's Avatar
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    I buy the cheapest blades I can find for my cars since I almost never drive them in the rain, never in snow, and they are parked in the garage when not being driven. I figure I'm replacing them every spring anyway just so the windshield washer works decently. Under those conditions a $2 clearance one works just the same as an expensive one to clean bugs off the windshield.

    The truck I buy better ones for since it actually is parked outside and I need them to work in rain.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  19. #19
    Donating Member massacre's Avatar
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    Quote Originally Posted by sly View Post
    Yeah... batteries are really hit or miss from any manufacturer now. Sometimes you get 8 years from a walmart battery, sometimes 6 months and everything in between.
    I bought a yellow top Optima for my Zephyr. Been super happy with it. Even bought the fancy optima charger/maintainer too and was $$$ but am happy with the setup. Same yellow top will also fit my Mustang too so that's a plus.
    I heard that there are only like 2 manufacturers who make batteries in the US and everything is just rebranded
    ..

  20. #20
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    I always go with a Motorcraft for my Vic. I always go with a Motorcraft for my Vic. Mine's an 03 and I bought it in '08 with the factory battery in it. The next one made it 7 years and I just had to replace it this October. The last one died because the car sat so long due to covid and working from home. So 11 years on factory, 7 on the second (due to negligence) and now on battery #3.

    All my other cars run the Oreillys SuperStart Extreme batteries which are made by EastPenn/Dekka (a US manufacturer). They are not crap like most of the Johnson Control manufac. ones, which is what a lot of the other brands out there are. The superstarts can get pricy but the cost evens out vs. replacing a "cheap" battery every 2-3 years. Just my opinion tho.
    These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.

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