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Discussion Starter · #1 ·
I recently rebuilt my motor and installed it. Alt. is known to be good but isnt charging. Hooked up wire from battery to the field wire at the plug on the back of the alt. and it charges just fine. Where does the 12v source come from for the field wire to excite the regulator? Thanks.....Carter
 

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from the dash light. be sure the bulb is good and the connection is good. Several have reported that they have had connection problems in the instrument panel.

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Steve Wood

Growing old is mandatory; growing up is optional.


86 GN bought new, 87 T-type-81 El Camino with GN drive train-basically stock 86, 94 Caprice 9C1, 69 SS396 Camaro Convertible
 

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Discussion Starter · #3 ·
Steve, the alt was charging fine when the motor was pulled so i'm thinking small wires on the starter or maybe a fuseable link in that area.??? Is there any feed in that area? Anyway, i'll check the bulb in the dash and thanks....Carter
 

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fusible links on the starter...one goes to the fan, one goes to the lights, and one goes to everything else.

I am not looking at the diagram at the moment but a feed goes from the key to the light, to the field as I recall. Seems like in some, the light is the only connection but some may have a resistor or something around the light in case the light burns out.

Zap...you had this problem...what did you figure out?
 

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One day I had a little over two volts going to the field wire and it wouldn't charge. The next day after changing absolutely nothing I was getting around 6 volts to the field wire and it has charged ever since. I think it should be getting around 5 volts. I assume I had a poor connection somewhere due to the fact that the car had sat for a long while due to a busted windshield/expired inspection sticker.

I do know that for most GM alternators from 1974-1986 (I know cause I got a book with a chart) the field current @12volts is supposed to be 4-4.5 (volts I'm assuming although the chart doesn't say).

Mine would charge with the bulb burnt out, but mine is an 85 with a different type alternator etc.

I think if I understand what you are saying is that you hooked 12 volts up to the field wire. That used to be a big no-no, I have no idea if that still holds true. (Now maybe you are supposed to get 12 volts to the field wire with the newer charging systems, I have no idea). If it's still a no-no you may have fried something.


See if you can get Salvagev6 by email or otherwise. He is the resident alternator INTERNET EXPERT GURU.


[This message has been edited by Zap (edited July 19, 2001).]



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What year car is it? What alternator?

Anyway for a 1986-1987 CS144 alternator system, GN and TR, the Field Strobe current is obtained in the following circuit.

Gages fuse +12 volts to the volts lamp which has a brown output wire going through C100 the big terminal block under the wiper motor out to the generator terminal L.

After the car is running and the generator RPM increases the field strobe function is disabled and normal regulation occurs.

Sounds like a bad regulator inside the generator or else your volts lamp isn't wired correctly.

Good luck.
 

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Discussion Starter · #8 ·
Steve, Zap,& salvageV6, thanks for the replies. This is on an 87 GN w/120 amp alt. I just assumed because i pulled the engine the problem had to be in the engine compartment since everything was fine prior to pulling it. Looks like i need to check the guages fuse,the wiring block under the wiper motor,the dash temp light and look for 4 to 6 volts at the field connector on the alt while hoping i didnt fry anything by hooking 12v directly to it. Will check these and post my results. My thanks to all....Carter
 

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Don't bother with the temp. light, check the volts light circuit.


The brown wire should have +12 volts or battery voltage on it key on with the plug off the alternator.

The regulator portion of the generator is relaceable by itself inside the unit.

Field strobe current is generated by a +12 volt signal through the lamp. I have no idea what the current used is however.
 

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Salvage has the right idea...pull the plug off the regulator, turn the key on and see if you have voltage at the plug.

If you do, then it is most likely the diode inside the alternator. If not, then its back inside as he detailed.

I use the electrical diagram section of the manual almost daily. the rest of it...about once a month.
 

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Discussion Starter · #11 ·
salvageV6, you are so correct. Volts light, not temp light circuit. I was a little tired last night. I will be checking it out in the morning. I was glad to see that the brown wire does indeed have 12V supplied to it as the possibilty that it didnt ment i could have done harm to the system. I have no doubt Zap has delt with this because he is always right on in his replys( Dont get a big head Zap) but i really didnt relize there were SO many differences in the 84/85 and the 86/87. Just shows your never too old to learn. I'll keep y'all posted and thanks....Carter
 

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Originally posted by kwik6:
I have no doubt Zap has delt with this because he is always right on in his replys( Dont get a big head Zap) .Carter

Drug Test! Janet Reno, where are you when we need you! This guy is probably a brain surgeon or rocket scientist in real life! Where is the prozac? Bring him down gently!

 

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Discussion Starter · #13 ·
Steve, you popped that reply in on me as i was preparing my reply. Again thanks for the input, and i will know more in the morning. BTW, great race between you and Zap, i think. hehehe.....Carter
 

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All of my old books (most of them stop at 1986) deal with 78 amp and less alternators and always say "NEVER APPLY FULL 12 VOLTS TO THE FIELD WIRE!" But things change, and Steve told me (when I was having problems with mine) that he was getting 12 to his. So that is that. Steve even changes his underwear once in a while.

I have learned to never assume when dealing with GM cars.


I can't get a hat to fit me now, my head is so big.



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Least I can say that I have never lost racing Zap!
 

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Discussion Starter · #16 ·
Damn Steve, you dont waste any time do you. Do you have anything special you put on your fingers to keep them from burning up along with the keyboard. BTW congrats on your 1000th post and keep up the good work....carter
 

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Discussion Starter · #17 ·
Zap last i heard you werent leaving the state. How the hell were you racing Steve in some remote part of Texas. Oh, i get it, you had a disguise. Would that be a BIG hat...lol and thanks again.....Carter
 

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He left here in a body bag and no one could recognize him on the way home either.
 

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Discussion Starter · #20 ·
You guys came through for me. It is 12V and now i have it. I have a connector at the field plug so i could switch between it and a volt booster for trouble shooting and it was a bad connection, so alt is charging fine now at 13.5V at idle. I did notice the volts light is barely lit and when i pull the field plug it goes out. What might this be? The alt is freshly rebuilt to a 140A with new rotor, stator, regulator, brushes, bearings, used comutator end and rec. rectifier. My alt was going bad and i wanted to raise the voltage since im running underdrive pulleys and i was told this was the way to accomplish it...thanks for your help guys...Carter
 
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