new alternator - battery light on, but still charging at 16v?

This is a strange one. The alternator in my Corsica died (still
charged I think, but the bearings were falling out of the back of it).
I put in a rebuilt one, and it seemed to work fine for half a day.
Then after lunch when I started it the battery light was on. I left it
there at home until I could check it out later that night.

When I started it that night, the battery light was NOT on, and
charging voltage was 14.something, where it should be. Then later that
night while driving around the battery light came on, and I could
notice the dash lights would dim a little with the turn signals, like a
classic low voltage problem.

But when I got it home and checked it with a voltmeter, it was reading
16 volts! The battery light was still on now.

The battery light doesn't come on for over voltage, does it? Even if
it did, regulators don't usually fail intermittently do they? So
maybe it's a bad ground? It's weird that it happened right after I
changed the alternator, though.

I know I tightened the positive cable to the alternator well. And the
3-wire harness going to the alternator was locked into place. I
checked the battery leads and they were tight at the battery, too.

So my next step was to check the grounds coming from the battery (maybe
take a jumper cable and ground the battery myself) and the positive
cables at the starter/solenoid. Sound right?

Oh yea, the battery was new about 8 months ago and it's not a cheapie.
Thanks,
-Ryan

On 25 Jan 2005 10:42:27 -0800, wrote:

>This is a strange one. The alternator in my Corsica died (still
>charged I think, but the bearings were falling out of the back of it).
>I put in a rebuilt one, and it seemed to work fine for half a day.
>Then after lunch when I started it the battery light was on. I left it
>there at home until I could check it out later that night.

There is the high possibility that there is something wrong with the
rebuilt alternator you installed. If you have the receipt for it,
bring it back to point of purchase and get another one, IMHO !

Lg


>
>When I started it that night, the battery light was NOT on, and
>charging voltage was 14.something, where it should be. Then later that
>night while driving around the battery light came on, and I could
>notice the dash lights would dim a little with the turn signals, like a
>classic low voltage problem.
>
>But when I got it home and checked it with a voltmeter, it was reading
>16 volts! The battery light was still on now.
>
>The battery light doesn't come on for over voltage, does it? Even if
>it did, regulators don't usually fail intermittently do they? So
>maybe it's a bad ground? It's weird that it happened right after I
>changed the alternator, though.
>
>I know I tightened the positive cable to the alternator well. And the
>3-wire harness going to the alternator was locked into place. I
>checked the battery leads and they were tight at the battery, too.
>
>So my next step was to check the grounds coming from the battery (maybe
>take a jumper cable and ground the battery myself) and the positive
>cables at the starter/solenoid. Sound right?
>
>Oh yea, the battery was new about 8 months ago and it's not a cheapie.
>Thanks,
>-Ryan

Answers inline

> This is a strange one. The alternator in my Corsica died (still
> charged I think, but the bearings were falling out of the back of it).
> I put in a rebuilt one, and it seemed to work fine for half a day.
> Then after lunch when I started it the battery light was on. I left it
> there at home until I could check it out later that night.
>
> When I started it that night, the battery light was NOT on, and
> charging voltage was 14.something, where it should be. Then later that
> night while driving around the battery light came on, and I could
> notice the dash lights would dim a little with the turn signals, like a
> classic low voltage problem.
>
> But when I got it home and checked it with a voltmeter, it was reading
> 16 volts! The battery light was still on now.

Faulty regulator!

> The battery light doesn't come on for over voltage, does it?

Yes!

> it did, regulators don't usually fail intermittently do they?

No - what year/make/model/engine size would be helpful

> maybe it's a bad ground?

No

> It's weird that it happened right after I changed the alternator, though.

Duh! >>> some people make mistakes -- replacement alternator is possibly
defective!

> I know I tightened the positive cable to the alternator well. And the
> 3-wire harness going to the alternator was locked into place. I
> checked the battery leads and they were tight at the battery, too.
>
> So my next step was to check the grounds coming from the battery (maybe
> take a jumper cable and ground the battery myself) and the positive
> cables at the starter/solenoid. Sound right?

Pointless -- take the vehicle to a service station -- have them check the system
with their "VAT" or Voltage Amperage Tester!
This test can determine what the charging system may or may not be doing.

> Oh yea, the battery was new about 8 months ago and it's not a cheapie.

That's nice

> Thanks,

No problem
--
BBA
°?°
BBA's RC Site - http://www.billybadassrc.com
When Privacy Matters -- http://www.epic.org/

> No - what year/make/model/engine size would be helpful

1993 Corsica 3.1L V6. I just tested it again and it's putting out
14.8v at idle with no accessories on, and the battery light is off. My
Haynes manual says it should be between 13 and 14.5.

-Ryan

I hydrometer'ed the battery and it reads 3 out of 5 balls. This was
after I took it off the battery tender (it had been on for 24 hours)
and then started the car twice, letting it run for a few minutes each
time while I did testing.

Yes a low battery can cause the alternator to read high.... but when I
tested the battery last night without the car on it read ok voltage.
Also I had just taken it off the battery tender. But the battery
tender is only a .5amp charger I think. It's on my larger car charger
tonight.

-Ryan

> wrote in message
oups.com...
> > No - what year/make/model/engine size would be helpful
>
> 1993 Corsica 3.1L V6. I just tested it again and it's putting out
> 14.8v at idle with no accessories on, and the battery light is off. My
> Haynes manual says it should be between 13 and 14.5.

Perhaps your millimeter needs calibrating!

Try this -- Engine: On - Attach a voltmeter to battery terminals -- Now raise
the rpms to 1500. At the same time observe the voltage meter - any change?! --
No change - raise to 2500 rpm - if the voltage at anytime goes up and over 15
VDC -- possibly a faulty regulator!

You really need to perform a current draw test, JUST to be sure!

--
BBA
°?°
BBA's RC Site - http://www.billybadassrc.com
When Privacy Matters -- http://www.epic.org/

> > 1993 Corsica 3.1L V6. I just tested it again and it's putting out
> > 14.8v at idle with no accessories on, and the battery light is off. My
> > Haynes manual says it should be between 13 and 14.5.
>
> Perhaps your Multimeter <bah,damn spell checker!!!> not "millimeter" needs
calibrating!
>
> Try this -- Engine: On - Attach a voltmeter to battery terminals -- Now raise
> the rpms to 1500. At the same time observe the voltage meter - any change?! --
> No change - raise to 2500 rpm - if the voltage at anytime goes up and over 15
> VDC -- possibly a faulty regulator!
>
> You really need to perform a current draw test, JUST to be sure!
>
> --
> BBA
> °?°
> BBA's RC Site - http://www.billybadassrc.com
> When Privacy Matters -- http://www.epic.org/
>
>

> I hydrometer'ed the battery and it reads 3 out of 5 balls.


You have a hydrometer >> a specific gravity/battery acid temp reading would be
helpful! # Example: a specific gravity measuarment would read something like:
1.120 - 1.260 - 70F or 20C. The higher the better - 1.265 = Excellent Condition!
if the (battery charged) gravity were at 1.120 = poor condition.



--
BBA
°?°
BBA's RC Site - http://www.billybadassrc.com
When Privacy Matters -- http://www.epic.org/

It was the alternator. I took it back, got a new rebuilt one, and it
works fine now. Thanks for the help.

-Ryan