charging system woes

Hi Gang,

have a 94 shadow, 3.0L with 220K that's has an intermittent problem.
The alternator appears to quit charging. Upon starting the voltmeter
will stay at battery voltage, and it throws a code 12. The first time
this happened it only lasted a min or so, ie. after a few restarts it
went back to normal. For grins I had the local autozone guy cycle the
battery and test the charging system, all checked okay. Last night it
did it again, this time appearing DOA. The alternator again passed a
bench test at the local Autozone. Upon re-installing the alt, the
problem went away. Probing at the battery, I found 12.8 volts static,
and 14.5-14.8 when running. It had approx 2 volt drop when cranking.
With all accessories on voltage never went below 13-13.5volts.

Any thoughts?

Many thanks
Mike

 

Since you asked, here are my two cents:

Are all your electrical connections, including the PCM and engine/chassis
grounds clean and tight? How old is the battery and what condition is it
in? Was the battery bench tested out of the vehicle? If the alternator
checks out good and all the connections are also good, then I'd personally
suspect the battery may be going bad.

Bob

 

I believe the voltage regulator on that year is part of the PCM. They do go
bad sometimes. I would check the wiring from the alternator to the PCM for
any breaks and make sure all the connections are clean and tight.

 

With that many miles the brushes in the alternator may be worn to the
point that they are intermittent. You probably need to have the brushes
or the alternator replaced.

 

The numbers appear acceptable. At 220K (I assume miles, not kilometers),
your alternator may be near the end of its useful life. Brushes may be easy
to check/replace. If they're heavily worn, bank on the slip rings they ride
on being heavily worn as well. Just like with brakes, it's best to replace
brushes (shoes/pads) *and* turn the armature (drums/rotors).
Bryan

 

Hi,

the battery cells were low on electrolyte so i topped off with water.
Code 41 and code 14 are also being thrown. I guess I must start
checking wires and cleaning grounds. I will bench test the alternator
again to see if the code 41 pans out. I assume the field switching
circuits are in the alt?

Thanks for the ideas

Mike

 

It's normal for a vented lead-acid battery to lose some electrolyte -- you
just don't want (especially) the tops of the plates to be exposed to
atmosphere. What was the specific gravity of the cells before you added
water? A fully charged battery will exhibit a SG of about 1.26 at 68°F,
which should equate to a terminal voltage of about 12.65V (one hour or more
after being charged).

A charging system should be capable of producing enough power (or X current
at Y voltage) to prevent draining the battery at the worst-case load
condition. A voltage test by itself tells you only half the story. A
measurement of the load current will tell you how much current the
alternator needs to produce. Low (ie idle) speeds are the toughest test of
an alternator's output current capability.

Bryan

 

Code 41 is alternator field circuit open or shorted and is the one and only
code my 1992 Dodge Dynasty 3.3 threw during the entire time it was running
from purchase at 180,000 miles till I spun a rod bearing at 252,000 miles.
IIRC it threw that code at roughly the same mileage as yours. The fix was
to have a starter/alternator repair shop outside Unionville Missouri R&R the
brushes. That particular alt is the Denso 90 amp model and I am now using
it as a redneck battery charger by making my own adjustable voltage
regulator and driving it with an electric motor via the crank pulley and 4
rib alternator serpentine belt off of a 1989 Plymouth Sundance 2.2.