Is my alternator dead?

My car sat at the shop for two weeks while I had it wrapped and eventually the battery died.
When I got my car back, I had to replace the battery because it wouldn't charge after jump-starting the car. However I got a new battery and it still isn't charging, despite starting the car just fine.
Can an alternator just stop functioning from sitting around for too long?
I have a 2010 BMW 118d and yes the new battery was registered after being installed.

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  1. 1 month ago
    Anonymous

    Also forgot to mention, the battery dying from sitting still for two weeks was expectable. I have installed an an anti theft system with gps tracking and remote shut down, so it's always connected and consuming some energy

  2. 1 month ago
    Anonymous

    Sounds like you have parasitic draw to me. Do you by change have an aftermarket stereo unit?

    • 1 month ago
      Anonymous

      I do, changed it to an Android screen. The anti theft system causes this as well, but so far it only popped up an error code when I scanned for codes. Battery still charged just fine and I also upgraded from 80Ah to 95Ah to keep up with the added draw.

      Start your car. Take a multimeter. Put the prongs on the exposed parts of the cable, not the battery terminals.Check voltage.

      If you don't have >12.6V at the battery terminals while it's running, your alternator is toast

      I'll have to try this, so basically my readings should be 12.6 when car is running right?
      If I connect the multimeter to the red cable that comes out of the alternator, I should also get a 12.6v reading, meaning it's sending out the power to the battery, and if not that would mean it's not sending out power, right?

      • 1 month ago
        Anonymous

        Something is sucking juice when the engine isn't running.

        • 1 month ago
          Anonymous

          That I already know. But regardless of that, the alternator should be charging the battery when the car is running.
          I also thought it could be a faulty IBS module, but if it was that, itnwouldn't have been possible to register my new battery on it.

      • 1 month ago
        Anonymous

        A fully charged battery will read 12.6 or 12.7 volts while the car is off. While running you should see anywhere from 13 to 15 volts. If it's running and you don't have 13-15V, your alternator is not charging the battery.

      • 1 month ago
        Anonymous

        If you do have 13-15 at the alternator output stud but you have less than that at the battery, the power isn't making it to the battery, likely a damaged or corroded wire.

  3. 1 month ago
    Anonymous

    If you don't have >12.6V at the battery terminals while it's running, your alternator is toast

    • 1 month ago
      Anonymous

      Lol it should be like 13.6 volts

      • 1 month ago
        Anonymous

        Did you miss the greater than sign?

    • 1 month ago
      Anonymous

      Lol it should be like 13.6 volts

      Yup, 12.7 is where the battery should settle within an hour when it's full and not being charged or discharged. The charger should put out between 13.6 and 14.4 volts when running.
      Some old battery chargers might put out as much as 15-16 volts. Might have worked better in very cold conditions, but probably wasn't ideal for the battery. Maybe that's why batteries used to require water refills so often.
      Charger circuits made in this century might also adjust automatically based on temps, battery condition, etc. Pretty trivial stuff for modern power electronics.

      • 1 month ago
        Anonymous

        I heard for AGM batteries that voltage is lower, is that true?

        • 1 month ago
          Anonymous

          AGM and other gel batteries require a constant flat voltage, they really don't like the fluctuating output of a regular alternator

  4. 1 month ago
    Anonymous

    Start your car. Take a multimeter. Put the prongs on the exposed parts of the cable, not the battery terminals.Check voltage.

  5. 1 month ago
    Anonymous

    Well here's what happened.
    I tested the voltage on the alternator cable and it tested 12v. It only tested 12v because the tester I have is meant for batteries and only has 6v and 12v light and the 12v lit up.
    Battery also tested 12v but didn't show up as charging when the car started.
    So the alternator is working, the battery is working, but something happened in the middle and the power isn't getting from A to B. The battery is in the trunk while the alternator is in the engine that's at the front. Could it be a blown fuse?
    Also, I couldn't jumpstart the car from the front connectors, so I had to do it directly on the battery and it worked from there

    • 1 month ago
      Anonymous

      Don't ever jump start a bmw from the battery. You could fry module furthers up from the battery and or the voltage sensor on the negative terminal.

      • 1 month ago
        Anonymous

        I know, but the car wouldn't jumpstart from the front connectors.
        How do I check if I fried those components? I know for sure if I take it to BMW they're gonna quote me an absurd value and I want to make sure I actually need the parts they're going to quote me for

      • 1 month ago
        Anonymous

        This is for any new-ish car.
        God damn civics and corollas have ecms for door locks.

      • 1 month ago
        Anonymous

        Nothing of value would be lost in the process THO

      • 4 weeks ago
        Anonymous

        >he made the car start by applying ~14 volts to the battery cables and turning the key?
        >SHUT IT DOWN!
        Who writes this stuff?

        • 4 weeks ago
          Anonymous

          You could just say that you don't understand how modern vehicle electrical systems work. This has been common knowledge on a lot of cars made in the past 15 years. The jump start terminals are an isolated path away from the vehicle modules to prevent voltage spikes from frying them. learn to wrench.

          • 4 weeks ago
            Anonymous

            this. electrical systems in modern cars have the battery as a critical component. it acts as a line filter to filter out frequencies potentially harmful to communications and is also used as a shunt for spikes like you said.

          • 4 weeks ago
            Anonymous

            Voltage spiking from 0 to 14 fries your electronics? Sounds like a personal problem.

    • 1 month ago
      Anonymous

      Can't you get a multimeter easily? Even a $5 one would be better than an idiot light.
      Still, if the idiot light lit up at the alternator then it means the battery is connected to the alternator at least, no blown fuse in between.

      I have no clue how bimmer shit works but if it is a dumb old fasioned alternator then it needs 12v input on one of the thin wires to flash the field windings or it won't charge. If it's a smart alternator that the ECU controls then you're on your own.

      Just get a multimeter. 14.6v with the engine running, 12.6v with the engine off (fully charged battery) 12.0v is a flat battery.

    • 1 month ago
      Anonymous

      Get a multimeter - even the cheapest piece of chink junk from a hardware shop will do. Start the car and let in run for a couple of minutes. Take the mulimeter prongs and set them like pic related - if the voltage is bellow 13V it means you have a problem with the alternator. Most often then not it's the brushes that are the problem, but sometimes it might be the control module.
      If the alternator is working normally move on to the battery. Let the car run for for a while, like take a spin around the block, so the battery can charge a bit. Then, disconnect the battery from the car entirelly and take a measurment - this is for control purposes and it should show about 13v. Leave the battery disconnected for a couple of hours. Now after the battery has sat take another measurment - if the voltage is bellow 12 it means you have a dead cell and the battery does not have enough amperage to roll over the starter. Sometimes the problem can be fixed with adding distilled water, but most modern batteries are capsulated and braking the seal will void your warranty.
      Now another option is that the parasitic draw is too large for the battery to hold the charge - then you would have to start pulling fuzes.

      • 1 month ago
        Anonymous

        To continue a bit
        In order to check for a parasitic draw. Disconnect the positive connector of the battery. Take the multimeter and switch it from volts to amps(10amp pisition), and don't forget the change the position of the prong connectors - on the multimeter there is a prong position for 10 amps, that is where the red cable goes. Now connect the black prong to the negative terminal and the red prong to the car's positive harness. If the multimere reads anything above 0.08 you have a parasitic draw. Now to check which system is drawn power, keep the mutlimere connected as start pulling fuses - once you fall bellow the 0.08amps you've got the right circuit.

      • 1 month ago
        Kevin Van Dam

        MULTIMETER
        U
        L
        T
        I
        M
        E
        T
        E
        R

        Learn how to use it and be amazed what a $7 multimeter can diagnose.

        • 1 month ago
          Anonymous

          >"Hmmm infinite resistance on this wire huh? Would you look at that.."

  6. 1 month ago
    Anonymous

    you can take your alternator to a car store and they can test it for you.

  7. 1 month ago
    Anonymous

    Ask your father figure or the kids at the parts store wrenchlette.

    • 1 month ago
      Anonymous

      There's a huge difference between being a wrenchlet and an electrician, moron. Even the local shop here won't touch this kind of electronics because there's a whole bunch of modules in between the battery and the rest of the car

  8. 1 month ago
    Kevin Van Dam

    Also why did you post a turbo?

  9. 1 month ago
    Anonymous

    Voltage regulator failure was a common problem on e46 alternators. I would test it and see if it's working correctly.

  10. 1 month ago
    Anonymous

    Mam, you remove the positive cable with engine running and, if the engine dies, you need an alternator.

    • 1 month ago
      Anonymous

      >Mam
      *Man

      https://i.imgur.com/QWcnG3c.png

      My car sat at the shop for two weeks while I had it wrapped and eventually the battery died.
      When I got my car back, I had to replace the battery because it wouldn't charge after jump-starting the car. However I got a new battery and it still isn't charging, despite starting the car just fine.
      Can an alternator just stop functioning from sitting around for too long?
      I have a 2010 BMW 118d and yes the new battery was registered after being installed.

      Sorry OP. A blind fat thumb autocorrect typo. I wasn’t trying to be not funny.

    • 4 weeks ago
      Anonymous

      It's not 1970 anymore. Any modern vehicle will run like shit or just die if you do that even with a perfectly fine alternator.

      • 4 weeks ago
        Anonymous

        Boomer wives’ tale. It works the same as ever on modern vehicles.

    • 4 weeks ago
      Kevin Van Dam

      See

      It's not 1970 anymore. Any modern vehicle will run like shit or just die if you do that even with a perfectly fine alternator.

      If your engine is running it's probably dead. Or maybe the belt is loose and the alternator isn't actually turning. Or maybe it could be the brushes, which in that case if the alternator is serviceable you can replace them and if it's not, you'll have to get a new one

      Modern cars do not like running straight off the alternator. It’s not very clean power and all of the electronic BS in modern cars need that big battery to smooth out the power.

      OP here, really need some help figuring this out.
      Scanning for codes returns the following errors:
      4A66 - DDE: Power management, vehicle electrical system
      4A17 - DDE: Generator
      4A56 - DDE: Power management, battery
      4121 - DDE: DDE main relay

      Can this just be a bad ground or is my system fried? Alternator works, battery works. What's the issue? Voltage regulator? DDE relay fried? BMS fried?

      Get a fricking multimeter. Or charge up the battery, start the car, and go to the sensors- live data and find the voltmeter. If the car is running and you’re at like 11.5V, your alternator probably isn’t doing shit. Sometimes you can rev it and watch it go up to 12-13, but then it settles back low at idle, that’s a bad alternator.

      • 4 weeks ago
        Anonymous

        See

        Boomer wives’ tale. It works the same as ever on modern vehicles.

        • 4 weeks ago
          Kevin Van Dam

          Go do it. Busriders who haven’t changed out batteries or alternators on many cars wouldn’t know this.

          I have seen numerous cars cut out with batteries that drop cells too, they don’t even like running at like 11V. The dash will wig out and it will die randomly at idle. There’s a reason why some modern cars want the battery change to be done at the dealer, because the car’s computers and electronic bullshit is so picky that it needs to compensate for the battery age, whether it’s 3 months old or 3 years old.

          • 4 weeks ago
            Anonymous

            There is no battery when it is disconnected.

          • 4 weeks ago
            Kevin Van Dam

            Yea and a 10.7V battery sucking up alternator juice will be running at a slightly low voltage but not horrible and that is still way smoother than no battery at all.

          • 4 weeks ago
            Anonymous

            Idk what you’re going on about. I’m just saying that the alternator ain’t working all that great if the engine can’t run with the battery disconnected.

          • 4 weeks ago
            Anonymous

            >I have seen numerous cars cut out with batteries that drop cells too, they don’t even like running at like 11V. The dash will wig out and it will die randomly at idle
            If the battery's down to 11 V at idle, it's in a pretty poor state, and the voltage may dip very badly as soon as something turns on and draws more current from it.
            The regulators used to deliver power to the dashboard's processors and microcontrollers can handle some voltage swing, but they typically need a couple of volts more than what they're outputting. So if some part needs a stable-ish 5 V to operate, its input regulator might want 7 to 30 volts. If the input from the battery falls below that range even for a moment, the board may malfunction.
            Some microcontrollers do have a brownout failsafe that can halt and reset the chip if it detects out-of-spec input voltages, but if they don't, or it hasn't been set up properly, the controller may get stuck in a glitched state it was never supposed to end up in. Until you pull its fuse or disconnect the battery, that is.

  11. 1 month ago
    Anonymous

    if you stab a hole in the bottom of your gas tank with a piece of rebar and the engine stops after all the gas spills on your driveway, you need a new alternator

    • 1 month ago
      Anonymous

      You don’t even know how to be moronic.

  12. 1 month ago
    Anonymous

    My G35 alternator died this year after 19 years, but it was difficult to diagnose. Some alternators go into a simple mode, which triggers battery lights but will pass alternator tests, which mine did.

  13. 1 month ago
    Anonymous

    OP here, alternator appears to be working. Something between the alternator (in the front) and the battery (in the back) has fried.
    Now question is, considering I also tried to jumpstart the car from the back once, how fricked am I?
    Could this just be a blown fuse I can easily replace or is my entire electrical system fried? How do I even diagnose this before taking it to BMW so they can quote me 5k in unnecessary parts? Don't wanna spend too much on a cheap car

  14. 4 weeks ago
    Anonymous

    Not op,
    just measured my alternator and it's only registering less than a volt
    What do?

    • 4 weeks ago
      Anonymous

      If your engine is running it's probably dead. Or maybe the belt is loose and the alternator isn't actually turning. Or maybe it could be the brushes, which in that case if the alternator is serviceable you can replace them and if it's not, you'll have to get a new one

      • 4 weeks ago
        Anonymous

        Engine: running
        Belt: tight enough
        Alternator: spinning, albeit poorly (need to readjust the new pulley I put on)
        ordered a rebuild kit, so hopefully that solves it. Thanks for the help anon.

      • 4 weeks ago
        Anonymous

        Engine: running
        Belt: tight enough
        Alternator: spinning, albeit poorly (need to readjust the new pulley I put on)
        ordered a rebuild kit, so hopefully that solves it. Thanks for the help anon.

        Okay, I did some more research and since I've got a 5-pin alternator
        (denso 10241), one of them is an 'ignition'. (for context I'm fitting the alternator on a 70's car)
        Apparently, this 'activates' the alternator when you start the car. Otherwise you have to Rev up the engine past a certain rpm to get it activated.
        Will look into this further

  15. 4 weeks ago
    Anonymous

    OP here, really need some help figuring this out.
    Scanning for codes returns the following errors:
    4A66 - DDE: Power management, vehicle electrical system
    4A17 - DDE: Generator
    4A56 - DDE: Power management, battery
    4121 - DDE: DDE main relay

    Can this just be a bad ground or is my system fried? Alternator works, battery works. What's the issue? Voltage regulator? DDE relay fried? BMS fried?

    • 4 weeks ago
      Anonymous

      I think ya just need an alternator.

  16. 4 weeks ago
    Anonymous

    Isn't that a turbo?

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