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Old 09-01-2010, 01:52 AM   #1
jakvett
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Member#: 218841
Join Date: Jul 2009
Vehicle:
06 2.5i

Default Two Alternators in Two Years?!

I bought my 06 2.5i in 2008 with ~45,000 miles. I had it for about 3 months, and the alternator went out. I bought a new one (stock 75 amp), and it lasted until today. I wouldn't think that it would have gone bad this fast, seeing as I only put 25,000 miles on the new alternator. I am running a stereo system with 2 10" subs with 400 watts to each, and 75 watts to each of my 4 door speakers, but I don't play it overly loud. Obviously this puts extra stress on the alternator, but to me it seems excessive. Correct me if I'm wrong.

My question is, since I have to buy a new alternator anyway, should I go for the stock 75 amp, the STi 90 amp, or an aftermarket 160 amp like the one listed in the link below:

http://www.maniacelectricmotors.com/160amphioual1.html
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Old 09-01-2010, 02:17 AM   #2
razrielle
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Location: Wichita, KS
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where do you live? I know in florida I went through a new battery and a new alternator every year or so
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Old 09-01-2010, 10:06 AM   #3
kero
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SRP

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My wife's 05 corolla alternator went at 40K give or take, I don't think they make them they way they used to.

From what I read on other forums for other car makes, alternators in general don't last as long as they used to.
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Old 09-01-2010, 10:43 AM   #4
Bluefoton
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Join Date: Feb 2007
Chapter/Region: E. Canada
Location: Quebec, QC
Vehicle:
2008 2.5i-hatch -
now with a HID retrofit

Default

I'm still on my stock one....
With your stereo, you draw peak currents only for very brief moments of time, so it shouldn't affect the alternator. Do you have any battery issues? Just for the sake of it, check the voltage at idle with no load / under full load ( Maxed out fan, defrost, all headlamps and lights on...)
Maybe there is an issue with the belt being too strained and putting stress on the alternator as well?

Last edited by Bluefoton; 09-01-2010 at 10:52 AM.
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Old 09-01-2010, 08:49 PM   #5
jakvett
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06 2.5i

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Well I went down to Napa today, and when the guy looked through his alternator book, 05-09 Impreza/WRX/STi weren't even listed! He called his tech line, and they said they were working on em. Maybe they're having issues with those models.

Oh well, it was a Napa alternator, and it has a lifetime warranty so I won't pay a dime for a new one.
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Old 09-02-2010, 12:39 AM   #6
williaty
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Location: Delaware County, Ohio
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2005 2.5RS Wagon
Regal Blue Pearl

Default

jakvett, that's a BIG load on the stocker. You're devoting up to 50A just to your stereo. The alt is rated at 90A. Realistically, that means its long-term-survivable output is about 40-45A, at cold temperatures. If it's hot where you are, that number drops even lower. On my 2.5L, pulling 30A into the aux lights I have eventually killed the alt and made me have to upgrade to the Maniac 160A.
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Old 09-02-2010, 06:03 PM   #7
jakvett
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Dang, that's way more than I thought the stereo would draw. Thanks for the info. It rarely gets over 75 where I live, so the heat shouldn't be an issue though.

I picked up my alternator today, and it says 12v 110a on the top line, but some of the specs are 135a @ 6000 RPMS, and 110a @ 2000 RPMS. Is this considered a 135a alternator then? The one that just failed said 110 @ 6000 and 95 @ 2000, but the top line still read 12v 110a.
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Old 09-08-2010, 04:36 PM   #8
ederd2003
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when i had my 92 legacy i went through 3 alternators in 9 months... sometimes you just get unlucky. but each of mine expired at the cusp of warranty sooo... theres that
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Old 09-08-2010, 05:40 PM   #9
RaineMan
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Location: SL,UT
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Silver

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That is a crapload of electronics to be running on the little stock alternator. Buy an upgraded unit and a capacitor... they aren't too expensive.
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Old 09-08-2010, 07:42 PM   #10
Zefy
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Chapter/Region: VIC
Location: Coquitlam, BC, Canada
Vehicle:
1979 BRAT / 01 RSTI
99 2.5TS (DEAD) / 87 GL

Default

those power numbers came from where? is that peak or rms?

if you actually got an amp clamp meter you'd find that you're actually drawing substantially less than that. Even cranked you'll only peak at those numbers for fractions of a second.

if you have a stereo than that could mean that your wiring for the alt/battery has been messed with. give everything a good cleaning with emery cloth and such and see what happens.
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