alternator circuit question

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?)

On Fri, 19 Nov 2004 0051 GMT, "Jon G." <jon8338@peoplepc.com>
wrote:

>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
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

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
"Jon G." <jon8338@peoplepc.com> wrote in message
news:bTand.3200$Qh3.682@newsread3.news.atl.earthli nk.net...
> 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?)

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

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.
"maxpower" <gjbeasley@comcast.net> wrote in message
news:p4udnTKlpLgm3wDcRVn-qQ@comcast.com...
> 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
> "Jon G." <jon8338@peoplepc.com> wrote in message
> news:bTand.3200$Qh3.682@newsread3.news.atl.earthli nk.net...
>> 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?)
>
>

will that still set a fault for alt not switching properly?, If you bypass
the alt field in the PCM?
"Daniel J. Stern" <dastern@127.0.0.1> wrote in message
news:Pine.GSO.4.58.0411191302530.10472@alumni.engi n.umich.edu...
> On Fri, 19 Nov 2004, Jon G. wrote:
>
> > 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.

On Fri, 19 Nov 2004, maxpower wrote:

> 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