DaveW

The battery in my 91 XJ died yesterday. This was probably due to
draining it throughly 6 months ago when the fuel pump went out and then
leaving the dome light on all night. After running around for a while,
it would restart fast, indicating that while the battery was being
charged, it would not hold the charge overnight.

For the first time in my life, I actually got a replacement battery for
free from Auto Zone, as it was 4 days before the 3 year free replacement
warranty was out. But I digress.

Prior to the failure to start on Monday morning, it had been obvious
that the battery was going south. Very slow cranking in the mornings,
very slow power window unless the engine was on. But the amp meter never
went much to the charge side, just stayed in the middle.

My pervious XJ (a 92) did nearly the same thing a few years ago. I was
sure I needed an alternater, but bringing it into the shop, they said I
only needed a battery. Replaced that and I was happy for the next two
years until I sold it.

In every vehicle I've ever had before with a marginal battery, the amp
gauge would go way over to charge after starting.

Now, on the third start with the new battery, the gauge went about 1/3
of the way over to the charge side, indicating an healthy alternater.

What's going on ? Is it a Jeep thing?

Regards,

DAve

spsffan

Dave Milne wrote:
> agreed - an ammeter would be much more useful !
>
> Dave Milne, Scotland
> '99 TJ 4.0 Sahara
>
> "Will Honea" <whonea@codenet.net> wrote in message
> news:JxX2tWiP5BNp-pn2-mFZQHUB3PRcW@anon.none.net...
> : On Wed, 30 Jul 2003 04:36:19 UTC DaveW <spsffan@verizon.net> wrote:
>
> : attery but comes off the firewall. For most purposes, the voltmeter
> : is a glorified idiot light.
> :
> : --
> : Will Honea <whonea@codenet.net>
>
>

Yes, voltmeter. Factory stock. But it is supposed to show charging
verses discharging, right? Every non Jeep vehicle I've ever had would go
pretty far over to the charge side with a weak battery and a good
alternater after the engine starts.

Could well be a dash ground problem. As long as everything seems to work
okay (thrid day on the new battery and it still cranks the starter fast)
I will leave things be.

Regards,

DAve

Will Honea

On Thu, 31 Jul 2003 03:04:18 UTC spsffan <spsffannospam@verizon.net>
wrote:

> Dave Milne wrote:
> > agreed - an ammeter would be much more useful !
> >
> > Dave Milne, Scotland
> > '99 TJ 4.0 Sahara
> >
> > "Will Honea" <whonea@codenet.net> wrote in message
> > news:JxX2tWiP5BNp-pn2-mFZQHUB3PRcW@anon.none.net...
> > : On Wed, 30 Jul 2003 04:36:19 UTC DaveW <spsffan@verizon.net> wrote:
> >
> > : attery but comes off the firewall. For most purposes, the voltmeter
> > : is a glorified idiot light.
> > :
> > : --
> > : Will Honea <whonea@codenet.net>
> >
> >
>
> Yes, voltmeter. Factory stock. But it is supposed to show charging
> verses discharging, right? Every non Jeep vehicle I've ever had would go
> pretty far over to the charge side with a weak battery and a good
> alternater after the engine starts.
>
> Could well be a dash ground problem. As long as everything seems to work
> okay (thrid day on the new battery and it still cranks the starter fast)
> I will leave things be.

A voltmeter tells you essentially nothing about the rate of
charge/discharge. It only shows the current voltage across the
battery (ideally). An ammeter will show the amount and direction of
current flow which gives you a decent indication of how much power is
flowing in/out of the battery. A battery that is essentially dead
with next to nothing for capacity will still read 13.8-14.2 volts even
if it only took a 1 amp charge for 30 seconds to get there. Sorta
like putting bricks in the toilet tank: the water still rises to the
same level in the tank but there ain't enough juice there to do ---- -
literally.

--
Will Honea <whonea@codenet.net>