# 120a alternator upgrade worth it?



## Lysholmrado (Oct 10, 2001)

I have a 03 GTI 1.8t and it has the 90a alternator. I am getting major dimming when I crank the system wide open. Does anyone with a similar setup have any experience upgrading to the 120a alternator from the mk4 VR6? Is there a drastic improvement? Is this a direct swap without modifcation?
jl 500/1 on a 10w7
jl 300/4 bridged on a set of boston pro 60 components
I have one of the bigger rockford fosgate amp kits not sure on the gauge. 
gains are all set according to JL manual.



_Modified by Lysholmrado at 1:46 PM 5-23-2007_


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## LETTERMAN52 (Jul 28, 2003)

*Re: 120a alternator upgrade worth it? (Lysholmrado)*

Have you upgraded your grounding wires in the engine bay?


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## Lysholmrado (Oct 10, 2001)

*Re: 120a alternator upgrade worth it? (LETTERMAN52)*

no i have not done anything but add the stereo to the car


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## Non_Affiliated (Feb 12, 2002)

*Re: 120a alternator upgrade worth it? (Lysholmrado)*

For the price of a OEM alt just go bigger.
http://stores.ebay.com/Iraggi-...onics
Dominick Iraggi of Iraggi Alternator
Dominick Iraggi
1-615-287-7991 Shop
1-615-594-8965 Cell
Just ask for Dominick
Or e-mail.
[email protected]
Just tell him Don (Non_affiliated) refered ya.


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## LETTERMAN52 (Jul 28, 2003)

*Re: 120a alternator upgrade worth it? (Lysholmrado)*

It is my belief that your grounds are inadequate. Not the ones for the amp but the ones for the battery.


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## Lysholmrado (Oct 10, 2001)

*Re: 120a alternator upgrade worth it? (LETTERMAN52)*

I will try the ground upgraded first then if that does nothing I will check out those alternators suggested.


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## Calinada (Nov 29, 2005)

*Re: 120a alternator upgrade worth it? (Lysholmrado)*

Iraggi Alts are definitely the way to go if you're going to upgrade. Talk to him and he'll let you know exactly what you need based on your situation.
If I had to guess I'd say you're running 4 guage to those amps. Pretty sure 8 would be too small and if you are running 8 you should upgrade.
As for the engine compartment the big 3 is always a good idea to upgrade.


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## Lysholmrado (Oct 10, 2001)

*Re: 120a alternator upgrade worth it? (Calinada)*

I looked at the main battery cable and it is 2 gauge wire. the rest is 8 gauge going to the amps and their grounds as well.


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## LETTERMAN52 (Jul 28, 2003)

*Re: 120a alternator upgrade worth it? (Lysholmrado)*


_Quote, originally posted by *Lysholmrado* »_I looked at the main battery cable and it is 2 gauge wire. the rest is 8 gauge going to the amps and their grounds as well.

It may be but what about the rest of the grounding wires. Alternator and so on?


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## Calinada (Nov 29, 2005)

*Re: 120a alternator upgrade worth it? (Lysholmrado)*


_Quote, originally posted by *Lysholmrado* »_I looked at the main battery cable and it is 2 gauge wire. the rest is 8 gauge going to the amps and their grounds as well.

Are you saying the guage going from the battery to the amp is 2 guage or the ground on the battery is 2?
Have the guage of the ground for the amp match the guage of your + to the amp. That should help.


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## 04VDubGLI (May 20, 2005)

I was curious to find out, did the big 3 fix the issue? I actually am very close to buying a 120A alternator for the same reason (though I'm only pulling 500w RMS). My lights will dim when I'm driving. 
Also, is there anything you need to do besides the physical swapping? Like... new grounds or anything?


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## gweedo (Nov 3, 2001)

*Re: 120a alternator upgrade worth it? (Lysholmrado)*

Definitely look at your ground wire first.
If you are still getting dimming, upgrade the alternator. I don't know if you can use alternators from other VWs in your GTI, but my W8 has a 150a alternator. 
I had a 90a in my GTI 337 with the exact same two JL amps and no dimming.... so I am guessing the ground is the key. I used some 0 gauge wire for my common ground in the rear of the car and a 0 gauge wire for the battery ground.


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## JDriver1.8t (May 20, 2005)

*Re: 120a alternator upgrade worth it? (gweedo)*

I have done the 120A alternator upgrade. I did it because I killed the 90A with 1300W RMS.
Here is the link to the Alternator DIY that I made in the MK4 forums.
http://forums.vwvortex.com/zerothread?id=2553076
It is a direct swap, and only takes a couple hours at most.
You need to upgrade your grounds. That will be the biggest help. If you have bad grounds, the alternator will do nothing for you.


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## 04VDubGLI (May 20, 2005)

*Re: 120a alternator upgrade worth it? (JDriver1.8t)*


_Quote, originally posted by *JDriver1.8t* »_I have done the 120A alternator upgrade. I did it because I killed the 90A with 1300W RMS.
Here is the link to the Alternator DIY that I made in the MK4 forums.
http://forums.vwvortex.com/zerothread?id=2553076
It is a direct swap, and only takes a couple hours at most.
You need to upgrade your grounds. That will be the biggest help. If you have bad grounds, the alternator will do nothing for you.

Thanks! Perfect... I'm going to redo my grounds and see what happens then. http://****************.com/smile/emthup.gif


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