I'm trying to eliminate as much under hood wiring as I can and need to know what the wires from the Alternator to the PCM are for.
On my car ('96) it's a Grey,F Field Signal,Gen Term C, and Brown,Gen L Lamp Signal,Gen Term B.
There is also a 5 volt ref. wire that goes into the C100 block and through the firewall. What's it for?
I'm trying to make sure I can eliminate the PCM completely so I can just run the Tec3.
Thanks...
"The FACTS are always subject to CHANGE once the TRUTH is applied"
"In the entire history of man the only stupid questions are the ones that don't get asked"
I don't have specific answers right now, but yes, the alternator is completely PCM controlled and won't charge correctly without the stock PCM.
I suggest calling an alternator rebuilder and seeing if they can swap out the "regulator" for an older style, real regulator thats not PCM controlled.
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Thanks Todd.
That's what I was afraid of. I just had the Alt. apart to get rewound and have the case polished.
If anyone know's what the 5volt ref. wire is for I'd like to know also.
"The FACTS are always subject to CHANGE once the TRUTH is applied"
"In the entire history of man the only stupid questions are the ones that don't get asked"
Could the 5 volt wire be for the VATs???
"The FACTS are always subject to CHANGE once the TRUTH is applied"
"In the entire history of man the only stupid questions are the ones that don't get asked"
the alt needs both wires to function properly
only thing to do would be to have the alt built as a 1 wire racing style , if its even possible
Ya,this sucks. 3 wires away from getting rid of the stock PCM and cutting out all that wiring harness.
"The FACTS are always subject to CHANGE once the TRUTH is applied"
"In the entire history of man the only stupid questions are the ones that don't get asked"
Found the 5 volt ref. It runs into the interior and back to the "Fuel Tank Pressure Sensor" where it's a Grey/Black stripe . So I don't need to worry about that one
. Now if I can get around the Alternator...
"The FACTS are always subject to CHANGE once the TRUTH is applied"
"In the entire history of man the only stupid questions are the ones that don't get asked"
Just got back from the alternator shop. The old guy (yea older then me) said that the grey wire is an exciter wire to tell the internal regulator in the alt. to "turn on" and the brown wire is just a power wire to turn on the charge light on the dash.
He said to just run a 12v feed wire that is hot in "RUN" to wake up the regulator to the grey wire on the alt. plug and call it a day. He said "Look around here. We don't have a computer for every car made setting around here. That's the way we do'em to test'em."
"The FACTS are always subject to CHANGE once the TRUTH is applied"
"In the entire history of man the only stupid questions are the ones that don't get asked"
I think he's wrong.
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Yeah. An alternator has a wire to turn it on. I had this problem with my 3400 swap as I didnt know what the wires were for.
You have the big red wire that goes right to the battery. Which has to stay, obviously. Then I only have 2 wires that go to the alternator (I used the plug from the 2.2 harness and put on the 3400 alternator and it works fine) One of the 3400 swap guys went off my pic too, and it seems to work for him too.
Above is my alternator. The red wire you need to run to something with a 12v + when the car is on. The gray wire must be for a guage, and it is not hooked to anything currently, doesn't seem to be necessary. One thing I also found out is not to hook the red wire to the fuel pump wire. It's only powered when the ignition is on, but it also seems to have some serious resistance or something when the car is off. My alternator started making a funny noise when the car was off, and after a little bit of time smoke started coming out of it.
Hope this is a bit of help.
every alternator produced from the early 70s to the mid-90s definitely followed that wiring scheme.
A large gauge red wire was the battery feed into the regulator to power the stator (electromagnet) and a brown "sensing" wire to activate and adjust output. The brown wire was key-on power through a dropping resistor (usually the warning bulb) and therefore runs a few thenths of a volt less than actual battery/output voltage.
But then GM switched to PCM controlled alternators and I do not have alot of info on them.
I know they are controlled by a 12v signal from the PCM that is likely PWM.
I know that connecting 12v to them will turn them on and will work on a test stand to test them.
What I am not sure is if there is a real volatge regulator in the alternator, or if the unit is just an elaborate relay controlled by the PCM.
If it is, then running a constant 12v to the terminal will turn the alternator fully and constantly on. This works for a bench test, but will over charge and kill the battery and computer systems in the vehicle.
I have no evidence that points one way or the other except for scan tool data which reports a duty cycle. But even scan tool data is not always real.
The real problem is that odds are about even that it could be either system if the PCM system actually exists as I describe it.
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guys, ive never seen a 'warning' light in my 98 come on, and ive had some MAJOR charging issues in the past... what's the deal? i KNOW the 2000+'s have a battery light that can come on because my dad's 00 did it once, but ive never EVER seen a low battery indicator or low charging output light come on in my 98. my car only puts out 11.76 volts at idle and ive got a 180amp alt, and the big 3. but the underdrive crank pulley has got to be why my charging system blows.
could that extra wire you guys are trying to figure out be for certain cars and not others? like 95-99 is different than 00+?
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What I am not sure is if there is a real volatge regulator in the alternator, or if the unit is just an elaborate relay controlled by the PCM.
If it's an "alternator" the voltage is internally regulated. Otherwise it would be a "generator". Besides INSIDE the unit, and even on a permanent magnet DC motor when you spin it, it makes AC power, and has to be converted back to DC for your car. The PWM i'm assuming is to help extend the life of the unit (by not having it on all the time) and to reduce load on the engine (more MPG, less emmissions) by not having it on all the time.
It may be possible to convert the alternator to a single wire setup, but then it kinda sucks when they're self exciting because you'll have to rev the engine a good ammount right when you start it so that it'll charge. And any time the thing shuts itself off.
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but ive never EVER seen a low battery indicator or low charging output light come on in my 98. my car only puts out 11.76 volts at idle and ive got a 180amp alt, and the big 3. but the underdrive crank pulley has got to be why my charging system blows.
could that extra wire you guys are trying to figure out be for certain cars and not others? like 95-99 is different than 00+?
The underdrive pulley will slow down the alternator so charging will not be up to par so much. Plus you've got a bigger alternator so it'll take a bit more speed to get itself to full charge. As far as the light.... just because it's there, doesn't mean it's going to work.
SHOoff wrote:
If it's an "alternator" the voltage is internally regulated. Otherwise it would be a "generator". Besides INSIDE the unit, and even on a permanent magnet DC motor when you spin it, it makes AC power, and has to be converted back to DC for your car.
If its an "alternator" it only means that it generates AC Current that is rectified (converted) back to DC. It has nothing to do with the regulator. For those who don't know, the rectifier is a bank of 6 diodes inside the alternator.
If its a "Generator" it produces DC and does not have rectifiers.
There are both internally and externally regulated alternators. The word alternator does not indicate anything about the regulator. Ford used externally regulated alternators into the 80s. GM began to phase them out in the 70s.
If you turn a permanent magnet DC motor it makes DC power, not AC.
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So to make sure everything is working right it sounds like I'm going to have to.
a) Run the stock PCM to control the Alternator output.
b) Try running a 12v ON source wire and see if the output can be regulated in the Alternator without frying something else.
c) Make up a new set of brackets and run a different style True 1 wire Alternator.
"The FACTS are always subject to CHANGE once the TRUTH is applied"
"In the entire history of man the only stupid questions are the ones that don't get asked"
why cant an alternator shop just use the stock case and put the one wire old style guts inside it?
john317(AKA Gary the Old guy) wrote:So to make sure everything is working right it sounds like I'm going to have to.
a) Run the stock PCM to control the Alternator output.
b) Try running a 12v ON source wire and see if the output can be regulated in the Alternator without frying something else.
c) Make up a new set of brackets and run a different style True 1 wire Alternator.
Mine works just fine with the ON wire connected to the fuel injector lead (i think that's where I put it, I'd have to check to be sure). It doesn't seem to overcharge the battery, otherwise it would have finished off the battery ages ago.
The alternator I pulled from the junkyard off a 3100 malibu had one wire going to the harness so I cute it and took it with me. I have to believe that they can be run from just that one wire since thats how it came out of the factory...
