alternator circuit question

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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?)
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wrote:

Check your car wiring diagram and locate the regulator.
...Jim Thompson
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On Thu, 18 Nov 2004 17:28:39 -0700, Jim Thompson

The engine control computer has the regulator built in, and an external regulator CAN be installed.
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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

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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.

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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
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On Fri, 19 Nov 2004, Jon G. wrote:

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

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On Fri, 19 Nov 2004, maxpower wrote:

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
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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

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On Fri, 19 Nov 2004, maxpower wrote:

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.
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Thank you DS..
I have now saved it in another place where I won't lose it !!!
Ted
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On Fri, 19 Nov 2004, me! wrote:

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

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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
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| Analog Innovations, Inc. | et |
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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

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What brand of car? Yugo ?:-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
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Citroen (SP?) did well lasted a long time, have a reno now, exloded last week, ah off topic again....
Chris

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