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High output FD Alternator

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Old 02-15-09, 01:56 AM
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High output FD Alternator

My alternator went bad recently, and I had a full rebuilt by a local shop, and it looks like its now more powerful then before. I didnt ask them to increase the power, but im not complaining! The rebuild was $125, and when I looked at my receipt, it said: Maximum output: 127 AMPS.

My headlights are noticeably brighter at night, and when I roll down the power windows at idle, they roll down at lightning speeds! I got a lot more then I bargained for.
Has anybody else ever experienced anything like this with higher output alternators?
Old 02-15-09, 02:20 AM
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Well considering it was a 15 year old alternator before the rebuild, wouldn't it make sense it would be stronger then before

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Old 02-15-09, 03:38 AM
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You just didn't notice it getting weak .01% per day, until it finally failed.
Old 02-15-09, 08:08 AM
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The stock unit runs a minimum 100 amps anyway...I suppose a "maximum output: 127 amps" is pretty much normal.
High output alternators, like those used by cop cars and stereo junkies, start at 150 amps and go to 300 or even higher.
Old 02-15-09, 08:21 AM
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I had the stock one rebuilt ,rewound to put out 150 amps .The GM alt with internal fan that I am running now starts at 90 ampe and puts out 190 at the top end.It is mounted with steel brackets and hidden belt adjuster that I made .The alt rebuilders business is building alts for sound off comp cars and high end sound systems.
Old 02-16-09, 02:37 AM
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Is it bad to run a higher output alt, then stock?
Old 02-16-09, 03:25 AM
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I wouldn't complain.
Old 02-16-09, 08:40 AM
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Originally Posted by FD3S-K
Is it bad to run a higher output alt, then stock?
The main fuse is 120 amps. You might have to upgrade some wiring and at least get a fuse rated for higher amperage.
Old 02-16-09, 08:51 AM
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while it is possible that you may run into a current issue on some high draw items and thus burn a wire or two, it far more important to get a volt meter and check the voltage of the Alternator. A high voltage from the alternator will fry you electronics...bad
Old 03-05-09, 06:05 PM
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Originally Posted by GARCO MOTORWORKS
I had the stock one rebuilt ,rewound to put out 150 amps .The GM alt with internal fan that I am running now starts at 90 ampe and puts out 190 at the top end.It is mounted with steel brackets and hidden belt adjuster that I made .The alt rebuilders business is building alts for sound off comp cars and high end sound systems.
Other than the tensioner did it bolt right up? I'll probably be in the market soon and i'm trying to avoid the 15 year old import fee.
Old 03-05-09, 06:50 PM
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Originally Posted by FD3S-K
Is it bad to run a higher output alt, then stock?
No, modern alternators are produce on demand, no "excess" current will be made unless it is required.


Originally Posted by ObliqueFD
The main fuse is 120 amps. You might have to upgrade some wiring and at least get a fuse rated for higher amperage.
Please do no do this, the electronics and accessories of your car will pull no more than required. refer to ohms law if in doubt. for example, I have a standard 12 volt system. I have an accessory that draws a nominal 4.5 amps at 13.5 volts. (most systems run about 13.5~14.7 as standard operating range)

I=V/R (or for those measureing in watts vice ohms) I=W/V so for sake of discussion take a head light; if you have a constant 12 volts, and a bulb that has a rating of 55 watts, you current consumption is going to be 4.5 amps this is an oversimplified explanation, however you will see that it cannot draw more than the required 4.5 amps unless something else (watts, or voltage) changes.


Originally Posted by Doc-1
while it is possible that you may run into a current issue on some high draw items and thus burn a wire or two, it far more important to get a volt meter and check the voltage of the Alternator. A high voltage from the alternator will fry you electronics...bad
Once again see above explanation, the electronics cannot "pull" any more amperage than what is originally allowed for in their design, unless you change something.

If you modify the system in some form, then it "might" require a change in the wiring, or fusing, but this is dependent upon what parameters you changed.....IE: swapping the stock fuel pump for a high flow nippondenso, or walbro unit, higher flow requires either the amperage to increase, or the wattage of the pumps motor to increase (actually it requires both, hence the usual fuel pump relay, rewireing mod that many of us perform to get more out of the pump) not that it was or is dangerous per se to use the stock wiring, just that a heavier guage wire can carry more current without the concurrent voltage drop imposed by the smaller wire; which then heats up until its reistance properties change, but that another subject.

if the OP noticed that his headlights were brighter, this is simply because up until this point his alternator was slowly failing and he failed to notice the differance over the time spread. kinda like waking up to a women you have dated for a year or two and suddenly noticing that she has gained 10 lbs, it happens over time.

sorry for the long winded explanation
kenn

Last edited by kenn_chan; 03-05-09 at 06:53 PM. Reason: speling owns me but the 7 does not
Old 05-13-12, 04:03 AM
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Absolutely agree. No need to upgrade any wires or fuses as long as you have stock electronic and voltage does not change. But if you add more electronic that draws more current then wiring from the alternator to battery has to be upgraded. It's the load that dictates how much current you are going to flow. Battery is the load when undercharged. Sorry to bring up this tread back from dead. BTW lots of cheap options HO alternators on Ebay. 160amp for $170. My only concern how much does it effect engine power.
Originally Posted by kenn_chan
No, modern alternators are produce on demand, no "excess" current will be made unless it is required.




Please do no do this, the electronics and accessories of your car will pull no more than required. refer to ohms law if in doubt. for example, I have a standard 12 volt system. I have an accessory that draws a nominal 4.5 amps at 13.5 volts. (most systems run about 13.5~14.7 as standard operating range)

I=V/R (or for those measureing in watts vice ohms) I=W/V so for sake of discussion take a head light; if you have a constant 12 volts, and a bulb that has a rating of 55 watts, you current consumption is going to be 4.5 amps this is an oversimplified explanation, however you will see that it cannot draw more than the required 4.5 amps unless something else (watts, or voltage) changes.


Once again see above explanation, the electronics cannot "pull" any more amperage than what is originally allowed for in their design, unless you change something.

If you modify the system in some form, then it "might" require a change in the wiring, or fusing, but this is dependent upon what parameters you changed.....IE: swapping the stock fuel pump for a high flow nippondenso, or walbro unit, higher flow requires either the amperage to increase, or the wattage of the pumps motor to increase (actually it requires both, hence the usual fuel pump relay, rewireing mod that many of us perform to get more out of the pump) not that it was or is dangerous per se to use the stock wiring, just that a heavier guage wire can carry more current without the concurrent voltage drop imposed by the smaller wire; which then heats up until its reistance properties change, but that another subject.

if the OP noticed that his headlights were brighter, this is simply because up until this point his alternator was slowly failing and he failed to notice the differance over the time spread. kinda like waking up to a women you have dated for a year or two and suddenly noticing that she has gained 10 lbs, it happens over time.

sorry for the long winded explanation
kenn
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