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    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, 05:07 PM.
    What I Own: 1993 Mercury Grand Marquis GS
    What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

    #2
    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

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      #3
      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.
      What I Own: 1993 Mercury Grand Marquis GS
      What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

      Comment


        #4
        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)
        Originally posted by gadget73
        ... and it should all work like magic and unicorns and stuff.
        Originally posted by dmccaig
        Overhead, some poor bastards are flying in airplanes.

        Comment


          #5
          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.
          What I Own: 1993 Mercury Grand Marquis GS
          What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

          Comment


            #6
            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).
            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 grandpa spec white and cranberry

            1984 Lincoln Continental TurboDiesel - rolls coal

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

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              #7
              Is it sealed or can you get to the cells? A cheap battey float type tester could easily help.
              03 Marauder DPB, HS, 6disk, Organizer Mods> LED's in & Out, M&Z rear control arms, Oil deflector, U-Haul Trans Pan, Blue Fuzzy Dice
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                #8
                I like to see over 14v when charging
                ..

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                  #9
                  Originally posted by massacre View Post
                  I like to see over 14v when charging
                  That's what I'd like to see.
                  What I Own: 1993 Mercury Grand Marquis GS
                  What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

                  Comment


                    #10
                    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!
                    What I Own: 1993 Mercury Grand Marquis GS
                    What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

                    Comment


                      #11
                      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!
                      What I Own: 1993 Mercury Grand Marquis GS
                      What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

                      Comment


                        #12
                        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)
                        Originally posted by gadget73
                        ... and it should all work like magic and unicorns and stuff.
                        Originally posted by dmccaig
                        Overhead, some poor bastards are flying in airplanes.

                        Comment


                          #13
                          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.
                          What I Own: 1993 Mercury Grand Marquis GS
                          What I Help Maintain: 1996 CV / 1988 CV / 1988 Tempo

                          Comment


                            #14
                            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)
                            Originally posted by gadget73
                            ... and it should all work like magic and unicorns and stuff.
                            Originally posted by dmccaig
                            Overhead, some poor bastards are flying in airplanes.

                            Comment


                              #15
                              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

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