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test alternator output?


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ice32 
Copper - Posts: 116
Copper spacespace
Joined: June 12, 2007
Location: Australia
Posted: November 10, 2007 at 8:15 PM / IP Logged  
Hey,
Is there anyway to test the output of a alternator, to see if it will still have enough power to charge a sound system?
Thanks
stang351w 
Silver - Posts: 350
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Joined: August 20, 2003
Location: Canada
Posted: November 13, 2007 at 8:12 PM / IP Logged  

Is there anyway to test the output of a alternator, to see if it will still have enough power to charge a sound system?

Thanks

well, first off, the alternator doesn't charge the sound system. it charges the battery which provides power to youe stereo. depending on what kind of power your running for your system would determine what you need to do, if it's just a small amplifier that only have 40 amp of fuseing, don't worry to much, but if your drawing 100+ amps to run your system then you need to consider some upgrades. if you have any doubt read up on upgradeing the "big 3" (stickyed at the top of this forum i beleive) and maybe upgrade to a ultima yellow top or some other deep cycle battery that would work in your aplication.

Tri County KustomZ
certified installer
zhalverson 
Copper - Posts: 180
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Joined: January 21, 2005
Location: United States
Posted: November 15, 2007 at 10:41 PM / IP Logged  
stang351w wrote:

well, first off, the alternator doesn't charge the sound system. it charges the battery which provides power to youe stereo. depending on what kind of power your running for your system would determine what you need to do, if it's just a small amplifier that only have 40 amp of fuseing, don't worry to much, but if your drawing 100+ amps to run your system then you need to consider some upgrades. if you have any doubt read up on upgradeing the "big 3" (stickyed at the top of this forum i beleive) and maybe upgrade to a ultima yellow top or some other deep cycle battery that would work in your aplication.

Well that's actually not true either.  When the alternator is working it would be charging the battery and providing current to your stereo.  The alternator will be operating at roughly 14 volts and that's what your amps will be operating at while the battery is only 12 volts.  This means your amps will be getting their power from the alternator and not the battery.  The only time the amps get their power from their amps is when the car is off or the voltage dips below 12 volts.

jmelton86 
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Joined: February 07, 2007
Location: South Carolina, United States
Posted: November 16, 2007 at 12:02 AM / IP Logged  

Can you simply hookup a DMM set to 'DC voltage' and rev the motor to see what amperage it peaks at (accesories off, of course)?

I actually always wondered this, just didn't think so since I haven't seen anything about it before.

2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001
i am an idiot 
Platinum - Posts: 13,579
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: November 16, 2007 at 5:01 AM / IP Logged  

Morning J   You can use a DMM on the voltage scale to see if the alternator is putting out Voltage.  To get the output current of the alternator it is a little more complicated.  That requires a clamp on DC current meter and a battery load tester.  Any reputable alternator shop will have the equipment needed.   Clamp the meter around the charge wire and connect the load tester to the battery.  When the load tester pulls the battery down the alternator will do its best to get the voltage back up to 13.8 thus producing all of the current it can.    

If you are using a DMM on the voltage scale, it is better to turn everything on, Lights, Air Conditioner, Stereo System Etc.   With all accessories on you will be demanding the most out of the alternator.  If it is able to increase the voltage when the motor is rev ved slightly, this ONLY means your alternator is working.  It will not tell you how much current it is putting out.

ice32 
Copper - Posts: 116
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Joined: June 12, 2007
Location: Australia
Posted: November 16, 2007 at 9:01 AM / IP Logged  
so if at a little above idle revs your alternator can still increase the volts.
it means that the alternator is doing its job with the current set up?
I'm just getting a terrible wine out of my alternator when i rev up and down, im thinking it is that i am drawing to much,
My dads a old mechanic and thinks it just needs a bigger compressor on it as he put a small one on it but it didn't do much (people didn't have "boom box's" in the boot in his day, so he dosn't believe its over drawing) but we will try that some time soon.
my system has 110A of fuse's but probably isn't drawing anywhere near that much at operating levels
and the alternator is 90A
Maybe a big 3 upgrade and a new battery is in order?
jmelton86 
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Joined: February 07, 2007
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Posted: November 17, 2007 at 3:14 PM / IP Logged  

i am an idiot wrote:
Morning J   You can use a DMM on the voltage scale to see if the alternator is putting out Voltage.  To get the output current of the alternator it is a little more complicated.  That requires a clamp on DC current meter and a battery load tester.  Any reputable alternator shop will have the equipment needed.   Clamp the meter around the charge wire and connect the load tester to the battery.  When the load tester pulls the battery down the alternator will do its best to get the voltage back up to 13.8 thus producing all of the current it can.    

If you are using a DMM on the voltage scale, it is better to turn everything on, Lights, Air Conditioner, Stereo System Etc.   With all accessories on you will be demanding the most out of the alternator.  If it is able to increase the voltage when the motor is rev ved slightly, this ONLY means your alternator is working.  It will not tell you how much current it is putting out.

Sweet. I work at a Napa attached to the side of a Carmax (we supply their parts) so I have access to the stuff. I'm actually on 'vacation' until Tuesday after next (weee!) so it won't be until then. Thanks.

ice32 wrote:
I'm just getting a terrible wine out of my alternator when i rev up and down, im thinking it is that i am drawing to much,
my system has 110A of fuse's but probably isn't drawing anywhere near that much at operating levels
and the alternator is 90A
Maybe a big 3 upgrade and a new battery is in order?

Big3, for sure. I think you're in the same boat as me. I've got 95a max system power (plus an extra Yellowtop) being powered by my stocker 105a alt and have been burdened by the dreaded 'whine' so I think i'm'a have to replace it. I do need to try one other thing first, though (outer sheild solder joint in my amp, thanks again- i am an idiot).

2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001
i am an idiot 
Platinum - Posts: 13,579
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: November 17, 2007 at 4:15 PM / IP Logged  
Hey Ice let me guess,  A Pioneer radio?
ice32 
Copper - Posts: 116
Copper spacespace
Joined: June 12, 2007
Location: Australia
Posted: November 17, 2007 at 6:31 PM / IP Logged  
you got it, I've read about there earth problem, should i try earth the rca and see if the whine goes away?
i am an idiot 
Platinum - Posts: 13,579
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: November 17, 2007 at 7:04 PM / IP Logged  
I would.   It will go away.
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