Two Alternators in Two Years?!

jakvett · 09-01-2010, 01:52 AM

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

* Registered users of the site do not see these ads.

razrielle · 09-01-2010, 02:17 AM

where do you live? I know in florida I went through a new battery and a new alternator every year or so

kero · 09-01-2010, 10:06 AM

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.

Bluefoton · 09-01-2010, 10:43 AM

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?

jakvett · 09-01-2010, 08:49 PM

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.

williaty · 09-02-2010, 12:39 AM

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.

jakvett · 09-02-2010, 06:03 PM

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.

ederd2003 · 09-08-2010, 04:36 PM

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

RaineMan · 09-08-2010, 05:40 PM

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.

Zefy · 09-08-2010, 07:42 PM

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.

09-01-2010, 01:52 AM	#1
jakvett Scooby Newbie Member#: 218841 Join Date: Jul 2009 Vehicle: 06 2.5i	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 * Registered users of the site do not see these ads.

09-01-2010, 10:43 AM	#4
Bluefoton Scooby Specialist Member#: 141373 Join Date: Feb 2007 Chapter/Region: E. Canada Location: Quebec, QC Vehicle: 2008 2.5i-hatch - now with a HID retrofit	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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09-01-2010, 02:17 AM	#2
razrielle Scooby Specialist Member#: 205698 Join Date: Mar 2009 Chapter/Region: MWSOC Location: Wichita, KS	where do you live? I know in florida I went through a new battery and a new alternator every year or so

09-01-2010, 10:06 AM	#3
kero Scooby Specialist Member#: 94299 Join Date: Aug 2005 Chapter/Region: Tri-State Vehicle: 2007 2.5i wagon mutt CGM	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.

09-01-2010, 08:49 PM	#5
jakvett Scooby Newbie Member#: 218841 Join Date: Jul 2009 Vehicle: 06 2.5i	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.

09-02-2010, 12:39 AM	#6
williaty Scooby Guru Member#: 71092 Join Date: Sep 2004 Chapter/Region: MWSOC Location: Delaware County, Ohio Vehicle: 2005 2.5RS Wagon Regal Blue Pearl	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.

09-02-2010, 06:03 PM	#7
jakvett Scooby Newbie Member#: 218841 Join Date: Jul 2009 Vehicle: 06 2.5i	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.

09-08-2010, 04:36 PM	#8
ederd2003 Scooby Newbie Member#: 219822 Join Date: Aug 2009 Chapter/Region: Tri-State Location: Central NJ Vehicle: 2003 Impreza RS Silver	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

09-08-2010, 05:40 PM	#9
RaineMan Scooby Specialist Member#: 256727 Join Date: Sep 2010 Chapter/Region: RMIC Location: SL,UT Vehicle: 2007 2.5I Wagon Silver	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.

09-08-2010, 07:42 PM	#10
Zefy Scooby Specialist Member#: 105104 Join Date: Jan 2006 Chapter/Region: VIC Location: Coquitlam, BC, Canada Vehicle: 1979 BRAT / 01 RSTI 99 2.5TS (DEAD) / 87 GL	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.