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Discussion Starter #1
I bought a brand new reman 94 amp alternator from autozone. I had them test it in the store and they said it was good.

well, here is my problem. with the car idling at 1000rpm, voltage at the alternator post is only 12.28 volts.

could anything else be wrong other than the alternator? its a 12si internally regulated
 

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you may need to rev the motor higher to get the alternator to register them remanufactor type alternators sometimes do that the exciter in it is set at a higher rpm than idle give it a rev and watch your volt meter jump up to 14 volts :yes:
 

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Discussion Starter #3
you may need to rev the motor higher to get the alternator to register them remanufactor type alternators sometimes do that the exciter in it is set at a higher rpm than idle give it a rev and watch your volt meter jump up to 14 volts :yes:
thanks . I wish that was the problem but its not. its a regular three wire alternator not a 1 wire. I looked back at a couple of my log files and even revving to 2000rpms, the voltage does not come up.
 

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It's not working correctly. Each cell of the battery will make around 2.2 volts X 6 cells. The battery should be at or near 13.2 volts the best I remember. If the alternator doesn't produce a minimum voltage greater than the battery has in it it will not charge the battery.
 

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thanks . I wish that was the problem but its not. its a regular three wire alternator not a 1 wire. I looked back at a couple of my log files and even revving to 2000rpms, the voltage does not come up.
it wasnt ment for a 1 wire :no: is this the same alt they came in the car or did you take out the external alt and put in the internal type
 

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Discussion Starter #8
Does the alternator require an ignition 12 volt input ?. Maybe this is not present on the proper terminal.

Are you sure that the meter you have is reading properly ?.

Jim
its a basic 12si alternator. I dont think it requires 12 volt input but I might be wrong. my undertanding was that it is self grounded, the main post goes to the charging stud, one small wire also goes to the charging stud to sense the voltage, and a final wire goes to the dash warning light. I have everything hooked up except that wire that goes to the dash.

I have three meters. a voltmeter gauge, a multimeter, and the built in gauge in megasquirt. they show almost the same thing
 

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Discussion Starter #9
It's not working correctly. Each cell of the battery will make around 2.2 volts X 6 cells. The battery should be at or near 13.2 volts the best I remember. If the alternator doesn't produce a minimum voltage greater than the battery has in it it will not charge the battery.
hi, the battery in fully charged condition puts out around 12.7 or so volts I believe. it is a brand new battery too. I think the alt might be bad.
 

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My Alt wasn't registering either...The white wire was pinched and it cut off the circuit..rewired it and all is good...
 

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its a basic 12si alternator. I dont think it requires 12 volt input but I might be wrong. my undertanding was that it is self grounded, the main post goes to the charging stud, one small wire also goes to the charging stud to sense the voltage, and a final wire goes to the dash warning light. I have everything hooked up except that wire that goes to the dash.

I have three meters. a voltmeter gauge, a multimeter, and the built in gauge in megasquirt. they show almost the same thing
It sounds like the altenator may be bad. It does require a resisted 12 volt source to entergize. It comes from the the dash light. If your dash light comes on when you start the car, IMO there is something wrong with the altenator.
 

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Discussion Starter #12
Ok, that makes sense. I did not realize that wire from the fuse box bulkhead was needed to energize it. Ill connect it tonight. Thanks

I took it to two autozones last night and they both tested it good. So it has to be that wire
 

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Discussion Starter #13
sorry, need to clarify something. are you saying the warning light has to be connected for the alternator to work?
 

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sorry, need to clarify something. are you saying the warning light has to be connected for the alternator to work?
Some alternators needs to know when the car is started. It usually gets the signal from the idiot light circuit. There are other ways of doing it, but it is the best way for internally regualted altenators.
 

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Discussion Starter #15
Some alternators needs to know when the car is started. It usually gets the signal from the idiot light circuit. There are other ways of doing it, but it is the best way for internally regualted altenators.
you are very right. I found this and it basically explains what you said, that the alternator needs the field current to initially energize. lol
for some reason I thought the field output was just a lamp output to the dash. lol

http://www.alternatorparts.com/understanding_alternators.htm

FIELD CURRENT SUPPLY

Field current supply is provided from two different sources - from the alternator itself, via the diode trio, and from the battery, via the alternator warning lamp. When you first get in the car and turn the key on, the engine is not running and the alternator is not spinning. At this time, the voltage/current source for the field current is from the battery, through the ignition switch, and through the warning lamp. After the engine is started, and the alternator is up to speed, the output of the diode trio is fed back to the regulator, and serves as a source of current for the field current.

 

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Discussion Starter #18 (Edited)
I think it is working now, because the ignition seems to be firing better(engine also running a lot leaner), and the car wont switch off when I turn off the ignition.

wtf?

someone tell me if this is wired incorrectly:

the ignition is wired to the battery through a relay that is activated by the ACC connection on the fuse box.

it should stop firing when I turn the key off right? well, the car wouldnt stop until I pulled the lead going to the distributor off the relay. whoa, scary.

any ideas? I would have thought maybe it was dieseling from being too lean, but it died instantly when I disconnected the hei, making me think the relay was somehow not switching off with the key switch when the alternator is energized.


IDEAS??? PLEASE



edit: ok, i found this
http://www.jeepforum.com/forum/showthread.php?t=571743

has anyone installed a 10si or 12si and had this problem? something about back feeding the ignition
 

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Discussion Starter #20
I needed to add a diode when I had the problem of the engine not shutting off with the ignition key. I had MSD ignition and it was in the trouble shooting instructions for it.
hey, thanks. I bought a couple from radioshack. how did you install them?
 
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