alternator circuit question

Discussion in 'General Motoring' started by Jon G., Nov 19, 2004.

  1. Jon G.

    Jon G. Guest

    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?)
     
    Jon G., Nov 19, 2004
    #1
  2. Jon G.

    Jim Thompson Guest

    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 Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    I love to cook with wine. Sometimes I even put it in the food.
     
    Jim Thompson, Nov 19, 2004
    #2
  3. Jon G.

    maxpower Guest

    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
     
    maxpower, Nov 19, 2004
    #3
  4. Jon G.

    me! Guest

    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
     
    me!, Nov 19, 2004
    #4
  5. Jon G.

    Sam Steele Guest

    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.
     
    Sam Steele, Nov 19, 2004
    #5
  6. The regulator is a part of the Single Board Engine Controller, yes.
    What you are calling "logic" wires are the field wires.
    <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.
     
    Daniel J. Stern, Nov 19, 2004
    #6
  7. Jon G.

    maxpower Guest

    will that still set a fault for alt not switching properly?, If you bypass
    the alt field in the PCM?
     
    maxpower, Nov 19, 2004
    #7
  8. 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
     
    Daniel J. Stern, Nov 19, 2004
    #8
  9. Jon G.

    me! Guest

    Thank you DS..

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

    Ted
     
    me!, Nov 19, 2004
    #9
  10. Glad to help (and this one posted today contained a much more complete
    list of usable regulators).
     
    Daniel J. Stern, Nov 19, 2004
    #10
  11. Jon G.

    maxpower Guest

    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
     
    maxpower, Nov 19, 2004
    #11
  12. Jon G.

    exxos Guest


    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
     
    exxos, Nov 19, 2004
    #12
  13. Jon G.

    maxpower Guest

    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
     
    maxpower, Nov 19, 2004
    #13
  14. 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, Nov 19, 2004
    #14
  15. 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.
     
    Daniel J. Stern, Nov 19, 2004
    #15
  16. Jon G.

    exxos Guest

    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, Nov 19, 2004
    #16
  17. Jon G.

    exxos Guest


    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
     
    exxos, Nov 19, 2004
    #17
  18. Jon G.

    Jim Thompson Guest

    [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
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    I love to cook with wine. Sometimes I even put it in the food.
     
    Jim Thompson, Nov 19, 2004
    #18
  19. Jon G.

    exxos Guest


    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
     
    exxos, Nov 19, 2004
    #19
  20. Jon G.

    Jim Thompson Guest

    What brand of car? Yugo ?:)

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    I love to cook with wine. Sometimes I even put it in the food.
     
    Jim Thompson, Nov 20, 2004
    #20
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