Re: alternator circuit question

From: Daniel J. Stern (dastern_at_127.0.0.1)
Date: 11/19/04 

Date: Fri, 19 Nov 2004 13:14:39 -0500

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.

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