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Idle voltage....Alternator?

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Damojo2003

New member
I have been keeping an eye on my voltage ever since I changed my tensioner 2 weeks ago. I noticed while the trans is engaged the voltage drops to just above 12v. I increase my rpms to see if that would help. As of right now I am idling at 750rpms. As soon as I hit the gas it goes up to 13.8 and slowly climbs to mid 14s. The volts are 14.6 when I cruise and 15volts at cold start up. I do have a electric water pump and an intercooler, but that should not be enough draw. I also have a stage 1 zzp alternator booster.

What do you guys think this is pointing at? voltage regulator, alternator or is this normal? Just want to be prepared for the possible cost before I bring it to autozone for testing.
 
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Electric motors pull more power more amps then you think.
The volt buster is not helping much either. From what i remember it takes away from ampers.

I would not worry about it untill you car starts to see below 12.5 while driving. Have your battery checked out. Your cars electrical really mainly runs off the battery. Alt is to charge the system
 
Are you sure the alt booster takes away from amps?

I did some reading and I think i am going to do the big 3. I have some older power wire from about 5 years ago that I used with an old system. Should be enough to do it.
 
Normal. As long as the volts are at 14 somethin when the rpms are at around 900-1000 rpm's you're fine.
 
Damojo2003 said:
Are you sure the alt booster takes away from amps?

I did some reading and I think i am going to do the big 3. I have some older power wire from about 5 years ago that I used with an old system. Should be enough to do it.
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make sure the wire is still good. 5 years is old. can get alot of condensation and mess up stuff inside the wrap.
 


Toofastgs said:
Your cars electrical really mainly runs off the battery. Alt is to charge the system
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Incorrect. When the engine is running the alternator is powering all systems at around 14.4V.

The battery is a 12V battery so it just sits there getting charged. It's potential is not enough to make it a power source in a 14.4V system, only a draw to be charged.

If the battery is what powers things, why can I take the battery out of a running car and it doesn't even notice?
 


Yes. 12's is normal when you're idling at 700 rpm's. I also idle at that and see the same thing. And if someone wants to argue with me saying my alternator is going out then aparently it's been going out for about a year now.lol.


I idle that low because of my cam and im sure you do for the same reason. So thats how i know.
 
Now if you're seeing 12 volts at 1200 rpm's directly off of the alternator then you may have some issues.
 
Im not so sure that is normal at idle. In order to charge, the alternator has to put out more voltage than the battery voltage of 12 volts. I dont recall ever seeing an alternator put out less than 13 volts at idle, normally its around 13.6 or so. With a voltage booster it should be putting out even more at idle.
 
SyntheticShield said:
Im not so sure that is normal at idle. In order to charge, the alternator has to put out more voltage than the battery voltage of 12 volts. I dont recall ever seeing an alternator put out less than 13 volts at idle, normally its around 13.6 or so. With a voltage booster it should be putting out even more at idle.
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I understand. But, There is no car in stock form that idles at 700 rpm's. I have a stage 2 voltage booster and still see right around that. No problems for over a year now. I'm sure if he would put the stock idle tables back he would be seeing the correct amount of voltage
 
TDCRacing said:
I understand. But, There is no car in stock form that idles at 700 rpm's. I have a stage 2 voltage booster and still see right around that. No problems for over a year now. I'm sure if he would put the stock idle tables back he would be seeing the correct amount of voltage
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Dude, my car idles stock at 650RPM. Most 3800s I've come across idle at ~700 +/-50 depending on the weather and cleanliness of the IAC.
 


TDCRacing said:
Ok then you tell us what the problem is.
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Faulty voltage regulator in the alternator or faulty alternator. It's simply having trouble maintaining voltage at idle. My car can maintain up to 15+ volts if the battery is low at 650-700RPMs idle. If it isn't giving you problems while driving, then it really isn't a big deal.

Though, I've seen this be a prelude to an alternator that just gives out. Can't say exactly when or even if. But it's possible.
 
Sabrewings said:
Faulty voltage regulator in the alternator or faulty alternator. It's simply having trouble maintaining voltage at idle. My car can maintain up to 15+ volts if the battery is low at 650-700RPMs idle. If it isn't giving you problems while driving, then it really isn't a big deal.

Though, I've seen this be a prelude to an alternator that just gives out. Can't say exactly when or even if. But it's possible.
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I was off on my accusation of the idle speed. And agree with you on your above statement. But for the record mine does the same thing....untill around 900 rpm's then it jumps to around 14. something
 
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