battery problem or alternator problem?

I have a 93 Nissan Sentra that will not start in the mornings as the
battery will be totally discharged. The car starts easily when I jump
the battery to another vehicle, and the battery charges reasonably
well if I let the car run for a half hour or so. But if I leave the
car off for more than a few hours (such as overnight) the battery is
again discharged and I need another jump.

This car is on its last legs and I do not want to spend the $300 it
will take to install a new alternator, but a new battery might make
sense if that is in fact the problem.

Based on this information is it possible to determine whether the
fault is in the battery or is it still possibly a faulty alternator?

ps when I turn the car off there are no lights left on to drain the
battery that I know of.

wrote:
> I have a 93 Nissan Sentra that will not start in the mornings as the
> battery will be totally discharged. The car starts easily when I jump
> the battery to another vehicle, and the battery charges reasonably
> well if I let the car run for a half hour or so. But if I leave the
> car off for more than a few hours (such as overnight) the battery is
> again discharged and I need another jump.

Sounds like the battery itself won't hold a charge, or the connections are
not well made.

> This car is on its last legs and I do not want to spend the $300 it
> will take to install a new alternator, but a new battery might make
> sense if that is in fact the problem.

Any number of places will do a load test for free.

--
Obama's childhood mentor, Frank Marshall Davis, was a communist.
http://www.aim.org/aim-column/print/...munist-mentor/

wrote in news:1342a8f9-16cd-43c4-8997-
:

> I have a 93 Nissan Sentra that will not start in the mornings as the
> battery will be totally discharged. The car starts easily when I jump
> the battery to another vehicle, and the battery charges reasonably
> well if I let the car run for a half hour or so. But if I leave the
> car off for more than a few hours (such as overnight) the battery is
> again discharged and I need another jump.
>
> This car is on its last legs and I do not want to spend the $300 it
> will take to install a new alternator, but a new battery might make
> sense if that is in fact the problem.
>
> Based on this information is it possible to determine whether the
> fault is in the battery or is it still possibly a faulty alternator?



You need a multimeter.

If the alternator is charging the system's running voltage will be about
13.5-14.4V. If the alternator is not charging, the system's voltage (engine
running) will be well below 13V.

To check for a dying battery: Turn on your dome light. Try to start the
car. If the dome light dims greatly or dims to nothing as the starter
engages, the battery is likely pooched.



>
> ps when I turn the car off there are no lights left on to drain the
> battery that I know of.


You could have some other key-off electrical draw. Any aftermarket
components installed? Radio, speakers, fog lights, remote start, alarm,
etc.?

Use the same multimeter as above to check for amperage with the key off. It
should be pretty much zero. Pull the negative battery cable and connect the
multimeter in series between the cable and the battery's negative post.

--
Tegger

> wrote:
>I have a 93 Nissan Sentra that will not start in the mornings as the
>battery will be totally discharged. The car starts easily when I jump
>the battery to another vehicle, and the battery charges reasonably
>well if I let the car run for a half hour or so. But if I leave the
>car off for more than a few hours (such as overnight) the battery is
>again discharged and I need another jump.

The voltmeter is your friend.

>This car is on its last legs and I do not want to spend the $300 it
>will take to install a new alternator, but a new battery might make
>sense if that is in fact the problem.

The voltmeter is your friend.

>Based on this information is it possible to determine whether the
>fault is in the battery or is it still possibly a faulty alternator?

No, you basically have no information right now. And it's also quite
possible that some load is discharging the battery when the car is
idle. You need to take voltage readings with the engine running and
with the engine off, then disconnect a battery terminal and measure
the current being discharged from the battery with everything turned
off.

If you have excessive load on the battery when the car is off, it's
then time to start pulling fuses until you find what is causing the
load. It COULD be the alternator pulling down the battery when it's
idle... but you don't know without putting the meter on.

>ps when I turn the car off there are no lights left on to drain the
>battery that I know of.

That you know of. That's the problem... there are lights like the
trunk light and the glove compartment light that you may never see.
Or maybe something else is drawing current. You have no idea until
you measure it. Get out the meter and measure it.

Almost certainly your battery is bad at this point, but you need to
identify what is causing it or you will quickly ruin a new one.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

the voltage across the battery should be about 13.2 volts with the
engine shut off. The voltage across the battery should be about 15
volts (or at least something higher than 13.2) with the engine
running. I am sure a place like Parts Source will test out your
battery and your alternator for no charge. Call ahead to make sure.
Ask if they can test it on the car or if you have to take it off. If
the battery is 5 years old it is probably on its last legs. they don't
last for ever.

On Feb 22, 11:32 am, wrote:
> I have a 93 Nissan Sentra that will not start in the mornings as the
> battery will be totally discharged. The car starts easily when I jump
> the battery to another vehicle, and the battery charges reasonably
> well if I let the car run for a half hour or so. But if I leave the
> car off for more than a few hours (such as overnight) the battery is
> again discharged and I need another jump.
>
> This car is on its last legs and I do not want to spend the $300 it
> will take to install a new alternator, but a new battery might make
> sense if that is in fact the problem.
>
> Based on this information is it possible to determine whether the
> fault is in the battery or is it still possibly a faulty alternator?
>
> ps when I turn the car off there are no lights left on to drain the
> battery that I know of.

Thank you for everyone's input. I have more information. I discovered
that the battery is in fact draining when the car is off. I
disconnected the ground terminal to the battery and connected an
ammeter between the neg battery terminal and ground to measure the
current drain, which is about 4 amperes. I went through the fusebox,
fuse by fuse removing the fuses and looking for the faulty circuit
(upon removing the fuse from the faulty circuit, the battery drain
should drop to zero). The result, sadly, is that none of the fuses I
removed affected the battery drain. So I am concluding that the short
in the circuit must be occurring somewhere before the fusebox. Does
this conclusion sound correct? Any advice?
Thanks,
-f

On Feb 23, 8:43 am, (Scott Dorsey) wrote:
> > wrote:
> >I have a 93 Nissan Sentra that will not start in the mornings as the
> >battery will be totally discharged. The car starts easily when I jump
> >the battery to another vehicle, and the battery charges reasonably
> >well if I let the car run for a half hour or so. But if I leave the
> >car off for more than a few hours (such as overnight) the battery is
> >again discharged and I need another jump.
>
> The voltmeter is your friend.
>
> >This car is on its last legs and I do not want to spend the $300 it
> >will take to install a new alternator, but a new battery might make
> >sense if that is in fact the problem.
>
> The voltmeter is your friend.
>
> >Based on this information is it possible to determine whether the
> >fault is in the battery or is it still possibly a faulty alternator?
>
> No, you basically have no information right now. And it's also quite
> possible that some load is discharging the battery when the car is
> idle. You need to take voltage readings with the engine running and
> with the engine off, then disconnect a battery terminal and measure
> the current being discharged from the battery with everything turned
> off.
>
> If you have excessive load on the battery when the car is off, it's
> then time to start pulling fuses until you find what is causing the
> load. It COULD be the alternator pulling down the battery when it's
> idle... but you don't know without putting the meter on.
>
> >ps when I turn the car off there are no lights left on to drain the
> >battery that I know of.
>
> That you know of. That's the problem... there are lights like the
> trunk light and the glove compartment light that you may never see.
> Or maybe something else is drawing current. You have no idea until
> you measure it. Get out the meter and measure it.
>
> Almost certainly your battery is bad at this point, but you need to
> identify what is causing it or you will quickly ruin a new one.
> --scott
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

Thank you for everyone's input. I have more information. I discovered
that the battery is in fact draining when the car is off. I
disconnected the ground terminal to the battery and connected an
ammeter between the neg battery terminal and ground to measure the
current drain, which is about 4 amperes. I went through the fusebox,
fuse by fuse removing the fuses and looking for the faulty circuit
(upon removing the fuse from the faulty circuit, the battery drain
should drop to zero). The result, sadly, is that none of the fuses I
removed affected the battery drain. So I am concluding that the short
in the circuit must be occurring somewhere before the fusebox. Does
this conclusion sound correct? Any advice?
Thanks,
-f

wrote:
> On Feb 22, 11:32 am, wrote:
>> I have a 93 Nissan Sentra that will not start in the mornings as the
>> battery will be totally discharged. The car starts easily when I jump
>> the battery to another vehicle, and the battery charges reasonably
>> well if I let the car run for a half hour or so. But if I leave the
>> car off for more than a few hours (such as overnight) the battery is
>> again discharged and I need another jump.
>>
>> This car is on its last legs and I do not want to spend the $300 it
>> will take to install a new alternator, but a new battery might make
>> sense if that is in fact the problem.
>>
>> Based on this information is it possible to determine whether the
>> fault is in the battery or is it still possibly a faulty alternator?
>>
>> ps when I turn the car off there are no lights left on to drain the
>> battery that I know of.
>
> Thank you for everyone's input. I have more information. I discovered
> that the battery is in fact draining when the car is off. I
> disconnected the ground terminal to the battery and connected an
> ammeter between the neg battery terminal and ground to measure the
> current drain, which is about 4 amperes. I went through the fusebox,
> fuse by fuse removing the fuses and looking for the faulty circuit
> (upon removing the fuse from the faulty circuit, the battery drain
> should drop to zero). The result, sadly, is that none of the fuses I
> removed affected the battery drain. So I am concluding that the short
> in the circuit must be occurring somewhere before the fusebox. Does
> this conclusion sound correct? Any advice?
> Thanks,
> -f
>

I would maybe check/unplug the alternator. They can internally short
and draw like that.

I don't know where your fuse links are, but usually the next step would
be to unhook those to ID which section of harness is the trouble one.
They are usually located at the end of the positive battery cable,
either on a power distribution box or starter.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com

> wrote:
>
>Thank you for everyone's input. I have more information. I discovered
>that the battery is in fact draining when the car is off. I
>disconnected the ground terminal to the battery and connected an
>ammeter between the neg battery terminal and ground to measure the
>current drain, which is about 4 amperes. I went through the fusebox,
>fuse by fuse removing the fuses and looking for the faulty circuit
>(upon removing the fuse from the faulty circuit, the battery drain
>should drop to zero). The result, sadly, is that none of the fuses I
>removed affected the battery drain. So I am concluding that the short
>in the circuit must be occurring somewhere before the fusebox. Does
>this conclusion sound correct? Any advice?

Sort of. The short in the circuit is occurring on something that is not
powered by the fuse box.

The number one offender in this case is usually the alternator. Disconnect
the positive lead from the alternator and see if the drain stops. (Be
sure to have the battery disconnected when you remove the positive lead
on the alternator since it's always hot.)

If that doesn't do it, your next step is to start looking for other things
that are powered through fusible links and not from the fuse panel, and
unfortunately this may require having a wiring diagram for the car to do
easily.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" > wrote in message
> Sort of. The short in the circuit is occurring on something that is not
> powered by the fuse box.
>
> The number one offender in this case is usually the alternator.
> Disconnect
> the positive lead from the alternator and see if the drain stops. (Be
> sure to have the battery disconnected when you remove the positive lead
> on the alternator since it's always hot.)
>
> If that doesn't do it, your next step is to start looking for other things
> that are powered through fusible links and not from the fuse panel, and
> unfortunately this may require having a wiring diagram for the car to do
> easily.
> --scott

I have been chasing a problem like this one in a Reatta for a couple of
years.
Upon shutoff, you can measure about 4 amps for several seconds, then it
usually
shuts down to a milliamp load. Point is, some systems do not go dormant
immediately,
and you dont need to be chasing ghosts. Let it stabilize before rushing to
conclusions.

In my case, sometimes the Reatta would hold a charge, and in other cases it
would
not start. One night, my wife woke me up and said the taillights on the
Reatta were
burning. So this intermittent taillight problem was probably the real
problem all along,
and the initial 4 amp draw was just a decoy.

I have had similar problems with an 89 Buick Regal, and traced it out for
weeks until
by luck I found the culprit. The seat belt retractor circuit was activating
intermittently during the night and was draining the battery. Finally
caught it in action, removed the
retractor circuit relay, and solved the problem (this system was not
necessary for safety.
It was a convenience/comfort item)