[Miata] Battery dead then live again??

[John Freas]

Previously on Battery, Butch Garcia <butchgarcia at earthlink.net> said...

I doubt if it is the ignition switch because the interior lights which
> aren't dependent on it didn't work.  What made me try to crank the engine
> with the old battery when I had the new battery in the box beside the car,
> was the fact that I accidentally shorted the battery on the positive
> terminal with another wire (careless but I thought the battery was dead) and
> it sparked.  The starter turned over very slowly but the engine caught on.
> It was ok thereafter.  The cranking speed was slow.  So was it the starter?
> but again, I mention the interior lights and radio and the buzzer when the
> ignition was turned on.... all these didn't work. The negative terminal is
> firmly anchored to the body and both terminals on the battery have good and
> clean and tight contacts.  The only thing I can think of is the wiring on
> the positive side to where ever it is connected to.. i.e. starter?
>

Hmm...  I'm getting that you didn't do the 2 amp charge, but rather tried to
work it like an ordinary car battery; jump starting it and then letting the
alternator charge the battery.  That really won't work for the AGM battery.
If it does anything at all it won't charge it enough to keep working, more
likely it will just generate heat in the battery instead of charging
anything.  In my experience the only thing that the alternator is able to do
is keep a healthy battery healthy.  If it is weak enough that it cranks
slowly, typically the alternator will *not* be able to keep it charged and
you will eventually have to put a charger on it to bring it up to a level
where it can.

That said, it sounds like there may be more than one thing going on with
your car.  Do you know what it was that discharged the battery the first
time?  Were the lights left on, or something like that?

If you want to keep the old battery under the assumption that it will still
hold a charge, then I'd put it on a 2 amp charge for 48 hours and then see
what happens from there.  If it fails again for no other reason, then the
battery is probably in need of replacement anyway.  If on the other hand,
the battery is holding a decent charge (or you replace it with new) and
you're losing power to the car, then you'll have to trace that through the
positive lead.  You'll probably have to look at a wiring diagram to figure
out exactly where the positive lead connects to other parts of the car, but
certainly it runs under the dash to the fuse holder, and to the starter
through a relay.  The other side of the relay is connected to the ignition
switch.

I'll keep my fingers crossed for you that the battery or its charge is the
issue 'cause chasing an intermittent electrical connection in an automotive
wiring harness can be a big job.

    -John
------------------------------
John Freas <%20john7690 at comcast.net>
1992 *YELLOW* "Sting<http://john.freas.home.comcast.net/pix/sting/sting.html>
"
1995 Black R Package
"Spike<http://www.geocities.com/clash_girl/Spike_Scrapbook.html>
"
Elizabethtown, Indiana
- Standard Disclaimer
<http://john.freas.home.comcast.net/disclaimer.html>Applies -
Team LS1,2, SP, the Gap...
I love my Miata
girl<http://www.geocities.com/clash_girl/Spike_Scrapbook.html>and my
Miata Baby
"I have no idea what those dimple things on the windshield frame are for."
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