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Charging Issue

Discussion in '2nd Gen. Tacomas' started by aviolette, Feb 21, 2013.

  1. Feb 21, 2013 at 3:17 PM
    #1
    aviolette

    aviolette [OP] Member

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    A couple of nights ago, I noticed my headlights were bright, then dim, then bright and then dim and so on. Eventually my battery light came on, then turned off, then back on...
    I plugged in my OBD2 Bluetooth ELM adapter, checked on my phone, and it showed that the voltage going to the ECU was only 12.6, then when my headlights would get normal bright again, the ECU was getting anywhere between 13.6 and 14.2.
    Alright, it's probably the alternator (most likely only the voltage regulator), I'm only at 80K, but it can fail. So I swapped it today.
    Started up the truck, battery light was on, and I have the same problem. Scan tool shows voltages between 11.9 and 12.8, occasionally it would jump back up to 14.0, all while sitting in the driveway idling.
    If the engine is running, the alternator should ALWAYS be putting out anywhere between 13.8 and 14.4, right?
    I was getting tires a few weeks ago, so I asked them to check the battery and alternator, tested OK, but this was before I started seeing the battery light.
    Anyone have any ideas of what might be going on?
     
  2. Feb 21, 2013 at 3:39 PM
    #2
    P9HST2

    P9HST2 Well-Known Member

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    How old is your battery? It may have a cell going bad intermittently. The alternator should be putting out those higher voltages while charging, but an internally shorted battery can cause havoc in the system if that's what's going on. If it's not the battery I'd suspect a bad connection somewhere.

    ETA: Check the voltages at the battery and alternator with a voltmeter to isolate further.
     
    Last edited: Feb 21, 2013
  3. Feb 21, 2013 at 3:58 PM
    #3
    aviolette

    aviolette [OP] Member

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    The battery is 5 years old. I tested with a volt meter at the battery and it aligns with the results I'm seeing on the scan tool,. Same type of fluctuations, like as if the alternator is working, then not working, working then not working. With a bad cell, wouldn't I be seeing the voltage drop below 11?
    Thanks!
    Adam
     
  4. Feb 21, 2013 at 4:01 PM
    #4
    aviolette

    aviolette [OP] Member

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    I should add that I've cleaned the battery terminals.
    I've also noticed that I'm only getting 14 volts at idle, as soon as I rev up the engine, the voltage drops.
     
  5. Feb 21, 2013 at 4:06 PM
    #5
    Geoff C

    Geoff C Active Member

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    Check for a loose ground somewhere. But at 5 years I'd replace the battery anyway.
     
  6. Feb 21, 2013 at 4:10 PM
    #6
    DriverSound

    DriverSound Señor Member

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    My oem battery lasted 27 months, regular use with no additional accesorries to drain it. I think 5 years of service, your battery had done its job.
     
  7. Feb 21, 2013 at 4:11 PM
    #7
    P9HST2

    P9HST2 Well-Known Member

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    I'd suspect the battery due to age and I'd replace it just to rule it out since it's time anyways. What does the battery voltage measure over a period of time with the engine off?

    When you rev the engine and the voltage drops, it may be because of a bad connection or because of an intermittent problem in the battery. Just my guess, but I'd replace the battery before I did anything else.
     
  8. Feb 21, 2013 at 4:13 PM
    #8
    aviolette

    aviolette [OP] Member

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    I can't seem to find any loose grounds.
    Does the ECU tell the alternator when to release power? Or is that all handled by the alternators voltage regulator?
    A few days before this started happening, I pressure washed the underside of the hood, the plastics on the top of the engine and the frame rails. I did avoid the firewall, battery, alternator and fuse boxes.
     
  9. Feb 21, 2013 at 4:15 PM
    #9
    aviolette

    aviolette [OP] Member

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    Before anyone gives me a hard time for washing under the hood. My excuse is that the top of the engine was covered in dirt and I was changing the spark plugs, so I wanted to be sure I wasn't going to get any dirt into the engine.
     
  10. Feb 21, 2013 at 4:17 PM
    #10
    aviolette

    aviolette [OP] Member

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    Okay, I'll get the battery replaced tonight.
    When off, it measures 12.6
     
  11. Feb 21, 2013 at 4:35 PM
    #11
    P9HST2

    P9HST2 Well-Known Member

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    The charging system is handled by the alternator and it's internal components, the only other parts of the system are the battery and the connections and fuses in between. I think you'll be pleasantly surprised when you replace the battery. If not, there's not much left to look for with a new battery and alternator.
     
  12. Feb 21, 2013 at 4:47 PM
    #12
    Ga tacoguy

    Ga tacoguy Well-Known Member

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    :) There is one other item that was not listed. The ECM or computer controls the voltage regulator. I would examine your wiring to and from the alternator to see if a wire is damaged. I do not know of a test for the alternator that doesn't require a factory tester. Do not do the remove the positive cable with the engine running to see if the engine stops. You will have a voltage spike from removing the cable and you will damage components that can not withstand a voltage spike. Good Luck
     
  13. Feb 21, 2013 at 4:54 PM
    #13
    Steves104x4

    Steves104x4 Well-Known Member

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    I thought flaring headlights means it's the alternator.
     
  14. Feb 21, 2013 at 5:18 PM
    #14
    aviolette

    aviolette [OP] Member

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    I replaced the battery, brand new battery, still the same issue.
    Anyone want to buy a truck?
     
  15. Feb 21, 2013 at 5:58 PM
    #15
    P9HST2

    P9HST2 Well-Known Member

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    I'm surprised the battery didn't fix it. Now with a new battery and alternator I think you'll just have to check everything else like the connections bit by bit with a meter.

    Check all of the connections with a meter, especially the high current ones between the battery, alternator, and the rest of the vehicle. Since the new battery must have a good stable voltage by itself, there must be a bad connection to the load causing it to flicker, unless there is a sort causing it to drop.

    You said you had to clean your battery connections. How bad were they?
     
  16. Feb 21, 2013 at 6:05 PM
    #16
    aviolette

    aviolette [OP] Member

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    It didn't take much effort to make them shiny, so it wasn't bad I guess. I also used a piece of sandpaper to clean the inside of the rings.
     
  17. Feb 21, 2013 at 6:15 PM
    #17
    P9HST2

    P9HST2 Well-Known Member

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    Just a rough idea of the things I'd try to measure with a meter, with the system running and acting up.

    Voltage across the battery posts. (Should be good - new battery)

    Voltage across the terminals connected to the battery. If not the same as the battery post voltages, check from each post to terminal, etc.

    Voltage from positive post to engine ground, body ground, etc.

    Voltage from known good ground to points throughout the power distribution.

    Divide and conquer, using a diagram from Chilton, Hayne's, or wherever available.
     
  18. Feb 21, 2013 at 6:26 PM
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    fireturk41

    fireturk41 I like to break shit!

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  19. Feb 21, 2013 at 6:26 PM
    #19
    aviolette

    aviolette [OP] Member

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    I actually have done similar tests and the voltages look to be about the same as what I get at the terminals, a little bit less, but not crazy. I also see the spikes when the alternator is actually charging the battery.
    It's very strange.
     
  20. Feb 21, 2013 at 6:28 PM
    #20
    P9HST2

    P9HST2 Well-Known Member

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    Then your battery and alternator assembly may be good, and the problem lies between that and your load, the rest of the vehicle. Divide and conquer, I know you can do it! :)
     
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