So i have a 91 legacy ls wagon. I am having extreme difficulty finding
what i beleive is some sort of a short in my charging system. I have a
pretty decent understanding of alternator and battery operations. I
have pulled the alternator out of the car and had it tested at the
local parts stores and voltage was up to par and i also replaced the
battery so they are both in working order. I took a my voltage meter
and tested the voltage of the battery when car is off (12.0v) and when
car is running (12.0 v) with all accesories off. I cant seem to pull
charge off the alternator. Also my abs,charge,and brake idiots lights
are on during any operations of the car which now wont start without a
jump. And sometimes the abs unit continues to run after car is turned
off. ANd on top of all of that my check engine light is on after car
gets up to running temp and after i connected the diagnoses wires the
code reads 35 which is purge valve solenoid failure. So my main
question is without the continuity of the purge control solenoid valve
working will that cause my alternator to not be able to charge my
battery therefore not allowing me to drive without replacing this part.
I would greatly appreciate any advice or knowledge that anyone could
share with me... cheers

91 suby wrote:

the alt. Anyway, try to confirm, when jumpstarting or starting from a
freshly charged battery - all the lights that should be on in the
cluster are on. I doubt the purge valve is part of the charging problem
- not positive.

Carl


--
to reply, change ( .not) to ( .net)

The purge control solenoid is a separate problem.

Your alternator should produce around 14.7 volts. 12 volts is just too
low. The electrical load on the system is draining the battery because
the alternator's output cannot keep up with demand.

Test the voltage with the engine running and all acc on. Bet that 12
volts drops to even less.

johninKY wrote:

thanks for the advice both of you

I am wondering if for some reason that when the alternator was tested
it was just starting to go bad and now it is completely gone . I guess
i will have to pull it again and take it to get tested. hopefully i
get some sort of info on the condition of the volts it is putting out.

"johninKY" <gflong (AT) nospam (DOT) kih.net> wrote

First off, those numbers are WRONG....FLAT OUT WRONG.
Lead acid batteries want to be floated at 13.80 to 14.20 volts PERIOD!
Too far under and they will sulfate, too far over and they will dissipate
the difference
as heat/gas.Don't guess on this shit! people might think you actually KNOW
what you are doing (you don't)
Now..onto Alternators...(check this against Wikipedia im sure they have a
section on this).
A alternator has three windings, all tied together in the center of a "Y".
in most alternators, this connection goes nowhere.
There are 6 diodes in two holders. 3 are positive and 3 are
negative.....pretty simple so far....
The 3 positive diodes go to the BAT terminal on the case, the 3 negative
ones go to the case internally. simple so far....
Here is the magic, the regulator. Some are internal INSIDE the Alternator
case, some are external..they both work the same.
The regulator requires 12 volts from a switched location (ign key). When 12
volts is applied to the Alternator and the engine is not yet running
this 12 volts SHOULD appear on the "R" or "Rotor" terminal.It takes about 3
amps to excite the 6 pole rotor mounted electromagnet.
If this terminal does not get 12 volts, the alternator will not produce
anything useable.This voltage is sent thru the two brushes located
at the end of the case near the end bearing cup. So much for the basics....
onto trouble shooting (for real..no magic numbers and double talk)
*IF* the 12 volts does not get to the alternator, NO POWER WILL BE
GENERATED.
*IF* some of the 6 diodes are blown, it WILL make some power, not enough and
more than likely will dump some AC crap
into the cars system and cause all kinds of trouble to show up (sound
familiar). Possible failures....
If you do not have 12 volts on the rotor terminal, check fuses marked
"reg,Charge,Alt,Engine" (buy service book or go look at one in AutoZone)
If you DO have 12 volts on the rotor terminal suspect regulator or diode
bridge. If you have bad diodes your AM radio will tell you..in the form of
"whine" or noise that was not there before(Engine running) Test for bad
diodes.....
Pull the plug on the back of the alternator, does all of the dash lights
look normal EXCEPT the battery light? if so you have a bad alternator.
Does the engine run correctly with the plug pulled? If yes..the alternator
is trashing the electrical system replace alternator. Next possible part..
"Fusible link" this is a nasty one to find, it looks like a regular wire,
BUT ITS NOT!!! it's a link, covered like a wire but designed to burn out at
a specific rating (60-100amps). The give-away is it has a nylon connector at
each end of it and is usually located close to the battery.
A real good way to pop one of these little bastards is to fully run down the
battery. Then jump start the car and drive the shit out of it.
The alternator will dump all its got into the battery (bad deal all around)
and will burn the link.Also check for a fusebox under the hood, this will be
a MONGO fuse, over 40 amps and large in size.Some cars use a relay in the
same box.The problem gets worse.
Some of the stuff in the car is fed from this very same location, now its
getting power from the alternator ONLY. Not from the battery, the voltage is
all over the place, its noisy, its too high, too low. The computer in the
car goes nuts!

Trouble shooting order....
(1) check at the BAT terminal on alternator with engine off for 12
volts.....
(2) turn key on, but do not start. Check Rotor terminal for 12 volts.
(3) with key on but not running check positive lead on regulator for 12
volts.
(4) start engine and let idle. Check voltage at battery AND BAT terminal on
alternator, should be the same.IF NOT you have an open link
or a bad wire/cable or rotten terminal.
(5) if you unplug the alternator and things get better (the voltage will
still be low) you have bad diodes.
(6) *NEVER EVER*...read this again... *NEVER EVER* disconnect a battery,
open a fuse link when the engine is running!
*THIS MEANS YOU!* When a alternator system loses it's battery it can and
will lose it reference for the regulator! the voltage can (depending on the
RPM) go as high as 18, even higher.Want to give all of your electronics the
"kiss of death"?? do this.

Do the tests, tell us what you finally find. The alternator is SIMPLE, few
parts...very few moving and not high tech.

Rastis P. Buttsnort wrote:

thanks so very much for this very thorough post

test 1 the voltage is the same
test 2 voltage the same
test 3 the voltage is the same
test 4 i jumped the car and it ran when i unplugged the alternator and
the voltage remained the same at the battery and battery terminal on
the alt

so what i conclude is that the alternator /(diodes), hence the blinker
noise coming from my speakers while i listen to my talk radio on AM,
have gone bad
Also while the car is running when i unplug the alt the battery light
goes off and when i plug it back in the light comes back on i dont know
what this means but maybe you do .

Thanks again for this much appreciated info

Sorry my "around 14,7 volts" comment so offended you. I'll make an effort
to be more specfic in the future.

John Long (my real name)

"johninKY" <gflong (AT) nospam (DOT) kih.net> wrote

14.7 volts..he would never do it.
He would think the regulator was bad, more bucks wasted.
If he actually DID get 14.7 volts, he would waste the battery and shorten
the life of the headlamps.
Devices that have pre-regulation wont be affected, but lamps really don't
care for over-voltage.
Batteries outgas like crazy when you take them above 13.80 Volts.

johninKY wrote:
Don't worry about it. Buttsnort is a self-appointed battery/alternator
"expert". He's mostly right but he gets rather excited when he sees the
infamous "14.7"

What really matters is that a good alternator will show a fairly rapid
rise on the battery voltage after starting.

I could go head-to-head on his statements and show him a few things but
it's not worth it.

"nobody >" <totally.bogus (AT) email (DOT) death.by.spam> wrote

I say "Show" him..if he is wrong you should challenge him!
I read his posts a while back, it makes sense. Where is he wrong?