Brand new battery, battery light still comes on and off

Discussion in 'General Motoring' started by adf, Feb 10, 2006.

  1. adf

    adf Guest

    Can anyone help me out please
    Car: 1991 Honda Accord Wagon

    OK after getting some advice I replaced the battery and put in a brand new
    one. Now the car starts and runs fine however, when the batter light is on I
    cannout use the alam/automatic unlock button in my key. The alam light stays
    ON. After driving a few blocks the battery light goes off and evreything
    seems fine.

    I am worried because this is what it did for the last week until yesterday
    when my car died and would not start. So I got a new battery.

    Why is the battery light coming on.

    adf, Feb 10, 2006
  2. adf

    Elle Guest

    Can you please get a multimeter and take DC voltage measurements at the
    battery terminals as follows?

    1. Engine off.
    2. Engine warmed up (like five minutes), idling.
    3. Engine warmed up, idling, with headlights, interior heater blower, and
    defogger on.

    See also the alternator check procedure at:

    How many miles and years are on your car's alternator?

    When you say "battery light," you do mean the warning light on the
    dashboard, don't you? Please describe the color of this light and any symbol
    appearing on it.

    How many batteries has this alternator gone through? How many of these
    batteries were permitted to die completely before replacement?

    Please answer as best you can the questions people ask of you. Otherwise,
    people are less likely to respond again.
    Elle, Feb 10, 2006
  3. adf

    adf Guest

    I will do a multimeter test later but I will answer the other questions you

    1) I am the second owner of the car so I don't know how many miles the
    current alternator has. The car has 115k miles total.

    2) Yes by batter light I mean the icon that looks like a batter with
    positive and negative markings lights up RED

    3) I have only owned this car since 2001 and this is the third battery since
    then. I don't much bother with checking the battery as the batter has a LONG
    warranty and the store that I bought it from just gives me a brand new one.
    That is what I did yesterday. Of the three only the first one was permitted
    to die completely I think.

    Can you tell me what you are getting at. I mean do you think the alternator
    is the problem? If so how have you come to this conclusion. I know
    information is limited as you don't have the alternator reads yet.
    adf, Feb 10, 2006
  4. adf

    Elle Guest

    This information helps a lot. These batteries you've been putting in have
    all been brand new, right? If so, this car is going through batteries much
    too quickly. You should be getting at least four years even out of a low
    quality battery. What the information below tells me is that the alternator
    is not putting out the amps needed to charge these batteries, indicating the
    alternator is worn. Most probable worn alternator part: The brushes. That's
    very common. Brushes tend to be a prime suspect when they have more than
    about 90k miles and several years on them. Also, keeping a battery until its
    charge is low (not necessarily dead, but just low), as you seem to have, for
    whatever reason, will wear down the alternator sooner. Google has
    information on this.

    Note that Tegger also suspected these. But we really need more information
    to confirm.

    So you may have had an alternator in need of new brushes for some time now.

    Autozone says they'll do an alternator check for free, but they have
    misdiagnosed my car's battery-charging-alternator system in the past, so I
    wouldn't trust them.

    What you're looking for with the voltage checks are the following

    1. Engine off: 12 volts.
    2. Engine warmed up (like five minutes), idling. About 14 volts
    3. Engine warmed up, idling, with headlights, interior heater blower, and
    defogger on. Voltage drops to about 13.6 volts or so.

    One can replace the brush assembly by one's self, if one is handy. has competitive prices.

    If you're tight on cash, I would minimize driving the car, because you're
    likely going to wear this battery down, and so have to buy another new one.
    Or, when you finally do get new brushes, they'll have to deal with a battery
    not in top condition.
    Elle, Feb 10, 2006
  5. adf

    Elle Guest

    FYI, on the battery light:
    "The battery light is misnamed: It doesn't go on when the battery is low.
    The battery light will go on only if the alternator is not charging the

    More at
    Elle, Feb 10, 2006
  6. To complicate things, in charging systems that were popular around the '80s
    brush failure would not turn on the charging/battery light because the
    current to turn the lamp on had to go through the brushes via the regulator.
    My '85 Volvo and the '84 Nissan I had were like that. More modern systems
    (including '91 Hondas, I'm sure) have a separate sensing circuit and don't
    have that blind spot.

    I concur - the alternator is very likely the problem, and the brushes (worn
    or oily) are the prime suspects. I also agree that the alternator may test
    okay on the bench depending on whether the intermittent is on again or off

    Michael Pardee, Feb 10, 2006
  7. adf

    TeGGeR® Guest


    Really? How dumb.
    TeGGeR®, Feb 11, 2006
  8. I guess they never gave it much thought. The lamp in those systems is
    essentially in series with the ignition power to the regulator input. As the
    alternator spins up it starts generating and part of that is fed to the
    regulator input, supplanting the ignition source and putting 12V on both
    sides of the charging light. If the alternator doesn't charge (like if the
    belt breaks) the light stays on as the regulator feeds the lamp current to
    the field. But if the brushes don't make contact, there is no place for the
    current to go to ground so the lamp doesn't light. I've wondered if a bad
    warning lamp means no juice to the regulator, but I've never tried it to

    I was lucky that both my cars that had that problem also had voltmeters. I
    noticed the voltmeter in each fluctuating as the brushes made contact and
    then didn't, but the lamps never flickered. (Sometimes they wouldn't come on
    before start-up when the brushes were wearing out.) Talk about "idiot

    Michael Pardee, Feb 11, 2006
  9. adf

    Elle Guest

    Would you say watching the voltage across the battery terminals of an idling
    car might also likely pick up bad brushes?
    Elle, Feb 11, 2006
  10. adf

    Doug McCrary Guest

    There's often more than one reason for a term to become popular....
    I dunno about MP, but it would better to watch at the alternator end. I think
    you'd see somewhat more fluctuation there due to the resistance of the circuit
    to the battery. Come to think of it, you'd do well to check both - big changes
    at the alt and small change at the battery could indicate bad wires or
    Doug McCrary, Feb 11, 2006
  11. That's how I caught it in both cases. The voltmeter fluctuated sharply
    between charging and battery voltage. I think the movement of the meter
    caught my eye as much as actual dash scanning did. At first it was only a
    couple seconds dropout at a time, worsening to a minute or so good and a
    minute or so bad within a week. In both cases the dropouts were worse when

    Michael Pardee, Feb 11, 2006
  12. adf

    Elle Guest

    I want to make sure I understand. These cars had a built-in voltmeter on the
    dash, and it was oscillating more than usual? Then you also took a portable
    voltmeter under the hood, connected it to the battery terminals, and watched
    the voltage at the battery terminals vary?

    I have started a site on "Battery & Alternator Tips" and want to include
    this or similar.

    Doug, I saw your post and agree there is at least a small advantage to going
    to the alternator itself for measurements to identify bad brushes. However,
    I am trying to devise some quick and dirty checks (if they exist) a
    layperson can do to identify likely failed brushes.


    (Not to supplant Tegger. His site is way more comprehensive. I am
    anticipating pre-emptively replacing my 91 Civic's brushes in a year or so,
    so I'm writing this up as much for that.)
    Elle, Feb 11, 2006
  13. Exactly right. The meters would show charging voltage (they weren't
    calibrated, of course, but we get used to what they read with the engine
    running and see what they read before starting) some of the time and
    not-charging voltage other times. That got my attention so I checked the
    actual voltages at the battery to see if the charging really was
    intermittent. Normally the meter in either car would be pretty steady until
    I turned the lights or the heater blower on - then it would only drop a bit.
    These were big changes.
    Looks good so far, Elle.

    I'm sure if the Volvo and the Nissan didn't have dash voltmeters I wouldn't
    have known anything was wrong until the battery gave me real trouble. I
    suppose I might have been lucky enough to see the headlights dimming a bit
    once in a while, but I dunno.

    Michael Pardee, Feb 11, 2006
  14. adf

    Elle Guest

    Good idea. I agree one might see the headlights dimming (or, really, any
    electrical funny business) with voltage dips as serious as that implied by,
    say, failing brushes.
    Elle, Feb 11, 2006
  15. adf

    theo.chan Guest

    Interesting post;

    I noticed the exact same problem crop up last week on my 1990 Honda
    Civic wagon. The red battery light on the dash would flicker
    intermittently ont the highway, and sometimes stay on as long as 5
    minutes. The battery is about year old. Now that I am back in the
    city, it may flicker a bit and come on for about 10 seconds.

    After a voltmeter test, it shows that the alternator is charging the
    battery fine when the engine is running, but under full load (radio,
    heater, defroster, lights), it is not. Is this something I should be
    worried about?
    theo.chan, Feb 12, 2006
  16. adf

    theo.chan Guest


    If the brushes are worn in my alternator, how long would it be until
    complete failure?
    theo.chan, Feb 12, 2006
  17. adf

    Elle Guest

    Can you do the five quick and dirty voltage checks at the site and report back?

    The voltage is supposed to drop, by design, when you add the loads you list.
    The question is how much it is dropping.

    Regardless, as you'll see from the commentary at the site above, your
    alternator system is highly suspect at this time.

    If it's the brushes (and based on posts here, I think that's a very high
    likelihood for a car your age), then I would get them replaced as soon as
    possible. For one thing, I think the car could leave you stranded any day
    now. For another, the condition is going to worsen until the battery does
    not charge fully. This does lower the battery's life.

    Can you share the battery history of this car, including jumpstarts over the
    years? Is the alternator the original, with original brushes?
    Elle, Feb 12, 2006
  18. Based on my experiences, I would estimate 1-2 weeks (somewhere around 10
    hours operation) from beginning of dropouts to almost never charging. Be
    aware the alternator diodes and windings are being overstressed from the
    surges to catch up in the meantime, though. I wouldn't recommend putting it
    off any longer than really necessary.

    Michael Pardee, Feb 12, 2006
  19. adf

    TeGGeR® Guest

    wrote in

    TeGGeR®, Feb 13, 2006
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