alternator circuit question

[Jon G.]

I have a 91 Plymouth Acclaim, and the alternator doesn't charge
the battery. I took the alternator out and had it tested, and
there's nothing wrong with it. I put a new battery in it, but
it still won't charge. I checked the fuseable link from the
alternator to the battery, and there is continuity. Therefore,
it must be the computer.

there are 4 connections on the alternator

L1: direct to battery, positive
L2: direct to battery, negative
c1: small wire, logic, to computer, activates diode
c2: small wire, logic, to computer, also battery ground.

I want to activate the alternator continuously and put on an
external voltage regulator.

What must the voltage (and current), to the logic inputs c1 & c2
be to do so?

I have in mind to run a potentiometer between L1 and c1, and
adjust it until the alternator kicks on.

The schematic shows that c1 goes to the coil of a transformer in
the alternator, which then goes to one of the diodes (an SCR?)

 

[Jim Thompson]

I have a 91 Plymouth Acclaim, and the alternator doesn't charge
the battery. I took the alternator out and had it tested, and
there's nothing wrong with it. I put a new battery in it, but
it still won't charge. I checked the fuseable link from the
alternator to the battery, and there is continuity. Therefore,
it must be the computer.

there are 4 connections on the alternator

L1: direct to battery, positive
L2: direct to battery, negative
c1: small wire, logic, to computer, activates diode
c2: small wire, logic, to computer, also battery ground.

I want to activate the alternator continuously and put on an
external voltage regulator.

What must the voltage (and current), to the logic inputs c1 & c2
be to do so?

I have in mind to run a potentiometer between L1 and c1, and
adjust it until the alternator kicks on.

The schematic shows that c1 goes to the coil of a transformer in
the alternator, which then goes to one of the diodes (an SCR?)

Check your car wiring diagram and locate the regulator.

...Jim Thompson

 

[maxpower]

the regulator is internal to the PCM, not external. been awhile since i
worked on this vehicle so i cant tell you the circuit numbers, but......you
have the 2 field wires, i believe they are both green wires...... with the
key on, car not running you should have battery voltage to one of those
wires, remember which one it is, now start the car, the other wire is going
to the PCM, if you ground that wire it will full field the alterator, that
will tell you if the alt is putting out... if it does start charging when
you do that..trace that wire back to the PCM and make sure it is a completed
circuit, assuming it is and the alt is not charging, replace the pcm, thats
a 100amp alt. i would not tamper or modify it in any way
Glenn Beasley
Chrysler Tech

 

[me!]

Best advice is to wait for Stern to pop his head in,,, he has written an
article on this specific issue... I just can't find it !! (Saved it
somewhere it wouldn't be lost) or.. I would forward it.. sorry.. however
hang on .. don't do anything silly in the interim..

Ted

 

[Sam Steele]

Blue supplies ignition switched battery voltage to the field circuit and the
green wire is the one used by the computer to ground and field the circuit.
You can splice in an external voltage regulator, being sure to ground it
against wherever you decide to mount it.

 

[Daniel J. Stern]

I have a 91 Plymouth Acclaim, and the alternator doesn't charge the
battery. I took the alternator out and had it tested, and there's
nothing wrong with it. I put a new battery in it, but it still won't
charge. I checked the fuseable link from the alternator to the battery,
and there is continuity. Therefore, it must be the computer.

The regulator is a part of the Single Board Engine Controller, yes.

there are 4 connections on the alternator

L1: direct to battery, positive
L2: direct to battery, negative
c1: small wire, logic, to computer, activates diode
c2: small wire, logic, to computer, also battery ground.

What you are calling "logic" wires are the field wires.

I want to activate the alternator continuously and put on an
external voltage regulator.

<etc>

The way you plan to do it will not work.

Here is a fix that *will* work, without replacing the engine computer and
without causing any additional problems:

First, pick one of the following regulators:

Regular normal electromechanical regulator:
NAPA Echlin VR32

Extra heavy duty electromechanical regulator w/vibrationproof mount:
NAPA Echlin VR34

Extra heavy duty electromechanical regulator w/vibrationproof mount and
convenient external voltage adjustment screw:
NAPA Echlin VR35, Standard-Bluestreak VR106

Transistorized regulator with no moving parts (no adjusting screw):
Standard-Bluestreak VR101, Wells VR706 (the wells item is very
inexpensive; it works but Wells doesn't make my favourite stuff)

Waterproof potted IC regulator with no moving parts (no adjusting screw):
NAPA Echlin VR1001, Standard-Bluestreak VR128


Any of these regulators will have two terminals on it, one marked "IGN"
and the other marked "FLD". (the VR1001 and VR128 have the "fld" terminal
on the end of a short wire lead). The alternator gets the original C1 and
C2 wires removed from its two field terminals (right next to each other,
small studs with nuts retaining the two flag terminals).

The regulator IGN terminal gets 12V via the ignition switch, and the "FLD"
terminal gets connected via a wire to one (either) of the field terminals
on the alternator. The other field terminal on the alternator gets
connected via a wire to ground. Run a ground wire -- 16ga is plenty --
between the regulator base and the battery negative terminal, and mount
the regulator such that it won't rock 'n' roll around. At this point, your
charging system will once again work fine. If you got the adjustable
regulator, set it for 14.2v across the battery with the engine fully
warmed up and ambient temperature above 50F.

If your "Check Engine" light comes on, put a resistor across the two
original field wires C1 and C2 before securing these wires such that they
can't ground out or get caught in any moving parts.

Close the hood; you're done.

 

[maxpower]

will that still set a fault for alt not switching properly?, If you bypass
the alt field in the PCM?

 

[Daniel J. Stern]

will that still set a fault for alt not switching properly?

Some SBEC calibrations won't care that an external regulator is doing the
job; others will set a fault. Of those that set a fault, some (mostly
'92-up) will illuminate the MIL. This can be worked around as previously
mentioned by putting a resistor across the vehicle's two original field
wires (which have been disconnected from the alternator). And really,
that's the only thing that matters, is that this repair be made in such a
manner as not to have the Check Engine light on. If it sets a fault code,
who cares? There are plenty of cases where an irrelevant fault is stored.
Cars without A/C routinely set a 33 ("Open or Short in A/C clutch
circuit"). K-car derivatives that have had the torque converter lockup
disconnected in accordance with the TSB on part-throttle surge and lug
will set a 37 ("Open or short in TCC circuit").

The important thing is that the charging system's operation will be
reliably restored without causing new problems, and at a much lower cost
than replacing the computer.

DS

 

[me!]

Thank you DS..

I have now saved it in another place where I won't lose it !!!

Ted

 

[Daniel J. Stern]

Thank you DS..

I have now saved it in another place where I won't lose it !!!

Glad to help (and this one posted today contained a much more complete
list of usable regulators).

 

[maxpower]

the reason why i ask is because the emiision test center cares here in MD.
I no all about those irrelvant codes, its hard to tell the emission test
center that the check engine lite is on becuase of a P/s switch is faulty,
but they dot care, they go by the guidelines, lite is on vehicle fails

 

[exxos]

I have a 91 Plymouth Acclaim, and the alternator doesn't charge the
battery. I took the alternator out and had it tested, and there's nothing
wrong with it. I put a new battery in it, but it still won't charge. I
checked the fuseable link from the alternator to the battery, and there is
continuity. Therefore, it must be the computer.

there are 4 connections on the alternator

L1: direct to battery, positive
L2: direct to battery, negative
c1: small wire, logic, to computer, activates diode
c2: small wire, logic, to computer, also battery ground.

I want to activate the alternator continuously and put on an external
voltage regulator.

What must the voltage (and current), to the logic inputs c1 & c2 be to do
so?

I have in mind to run a potentiometer between L1 and c1, and adjust it
until the alternator kicks on.

The schematic shows that c1 goes to the coil of a transformer in the
alternator, which then goes to one of the diodes (an SCR?)

I had a problem with one of my cars in the past with the alternator not
charging, what this turned out to be was the ground pin on the regulator was
going via a lamp on the dashboard, thus giveing a slight volt raise on the
ground so you got maybe 13V from the 12V regulator, though it took me a long
time to work out why my battery wouldn't charge, turns out the bulb went on
the dashboard, no ground on the regulator, alternator didn't charge the
battery, thus car wouldn't start.... strange how a small item such as a
dashboard light can stop the car from starting ;-)

Chris

 

[maxpower]

i would check out the circuit before cutting and adding resistors and
regulators, try to keep eveything working the way it was designed, many a
times i have found the 8 way connectors loose/corroded causing a no charge
condition. just a simple back probe test to the PCM

 

[Daniel J. Stern]

the reason why i ask is because the emiision test center cares here in MD.
I no all about those irrelvant codes, its hard to tell the emission test
center that the check engine lite is on becuase of a P/s switch is faulty,

That's why it's important to make sure the Check Engine light is not on.

You're making this much harder and "scarier" than it actually is.

 

[Daniel J. Stern]

I had a problem with one of my cars in the past with the alternator not
charging, what this turned out to be was the ground pin on the regulator
was going via a lamp on the dashboard, thus giveing a slight volt raise
on the ground so you got maybe 13V from the 12V regulator, though it
took me a long time to work out why my battery wouldn't charge, turns
out the bulb went on the dashboard, no ground on the regulator,
alternator didn't charge the battery, thus car wouldn't start....

Fun story, but not applicable to the original poster's '91 Acclaim -- not
even a little bit. Also, "12v" automotive voltage regulators have set
points of between 13.8 and 15.1 volts. A regulator with a set point of 12v
would not charge the battery.

 

[exxos]

Fun story, but not applicable to the original poster's '91 Acclaim -- not
even a little bit. Also, "12v" automotive voltage regulators have set
points of between 13.8 and 15.1 volts. A regulator with a set point of 12v
would not charge the battery.

I was suggesting that simple faults can make things look like sometime which
they are not, and yes you are correct 12V wont charge the battery, the OP
had alternator problems which im pretty sure I gave some suggestions towards
a possible cure. 12V regulators do exsist, like my old car raised to around
13V via the resistance in the dash lamp, the OP has a valuable new view
point on his problem to which I replied.

chris

 

[exxos]

i would check out the circuit before cutting and adding resistors and
regulators, try to keep eveything working the way it was designed, many a
times i have found the 8 way connectors loose/corroded causing a no charge
condition. just a simple back probe test to the PCM

assuming you replied to my msg, the lamp was part of those car diagnostic
"features", I think the idea was that if the regulator shorted out it would
light the lamp on the dash... only mine had a I/O short (at some point in
its life) so the lamp never lite, but yet the battery was charging to to
19V... It also doubled up to raise the regulator voltage to about 13V....so
much for technology..... good idea in theory though ;-)

chris

 

[Jim Thompson]

assuming you replied to my msg, the lamp was part of those car diagnostic
"features", I think the idea was that if the regulator shorted out it would
light the lamp on the dash... only mine had a I/O short (at some point in
its life) so the lamp never lite, but yet the battery was charging to to
19V... It also doubled up to raise the regulator voltage to about 13V....so
much for technology..... good idea in theory though ;-)

chris

[snip]

I think you'll find that the lamp was looking at the neutral
(mid-point of the "Y") terminal of the alternator, which is where most
idiot lights get their information... actually quite good at
indicating faults _before_ the battery goes dead.

...Jim Thompson

 

[exxos]

assuming you replied to my msg, the lamp was part of those car diagnostic
"features", I think the idea was that if the regulator shorted out it
would
light the lamp on the dash... only mine had a I/O short (at some point in
its life) so the lamp never lite, but yet the battery was charging to to
19V... It also doubled up to raise the regulator voltage to about
13V....so
much for technology..... good idea in theory though ;-)

chris

[snip]

I think you'll find that the lamp was looking at the neutral
(mid-point of the "Y") terminal of the alternator, which is where most
idiot lights get their information... actually quite good at
indicating faults _before_ the battery goes dead.

It was in the ground, I actually grounded the point instead of going via the
lamp, battery only got around 11V on it though at least it proved the point.
It was actually a 12V regulator, I measued it with a DMM at the time and
even at high revs it only ever hit 12.5V, so it needed a higher ground ref,
hence via the dash lamp. I would never have thought they would do such
tricks like that on cars, ive seen it countless times on electronics
equipment, though was supprised to see the same trick on a car.

Chris

 

[Jim Thompson]

i would check out the circuit before cutting and adding resistors and
regulators, try to keep eveything working the way it was designed, many
a
times i have found the 8 way connectors loose/corroded causing a no
charge
condition. just a simple back probe test to the PCM


assuming you replied to my msg, the lamp was part of those car diagnostic
"features", I think the idea was that if the regulator shorted out it
would
light the lamp on the dash... only mine had a I/O short (at some point in
its life) so the lamp never lite, but yet the battery was charging to to
19V... It also doubled up to raise the regulator voltage to about
13V....so
much for technology..... good idea in theory though ;-)

chris

[snip]

I think you'll find that the lamp was looking at the neutral
(mid-point of the "Y") terminal of the alternator, which is where most
idiot lights get their information... actually quite good at
indicating faults _before_ the battery goes dead.

It was in the ground, I actually grounded the point instead of going via the
lamp, battery only got around 11V on it though at least it proved the point.
It was actually a 12V regulator, I measued it with a DMM at the time and
even at high revs it only ever hit 12.5V, so it needed a higher ground ref,
hence via the dash lamp. I would never have thought they would do such
tricks like that on cars, ive seen it countless times on electronics
equipment, though was supprised to see the same trick on a car.

Chris

What brand of car? Yugo ?

...Jim Thompson