# testing alternator while in car
**URL:** https://forums.speedlife.net/t/testing-alternator-while-in-car/248617
**Category:** Shift518 Automotive
**Created:** [November 25, 2009, 7:48am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617 "2009-11-25T07:48:21Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@deadbeatrec](https://forums.speedlife.net/u/deadbeatrec)
#### Post date: [November 25, 2009, 7:48am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/1 "2009-11-25T07:48:21Z")
how can i do this?
i called pepboys and they say they have a scan tool that will run through the whole system. but i find it hard to believe that it will target the alternator specifically.
thoughts?
---
### Author:  [@ninety1two40](https://forums.speedlife.net/u/ninety1two40)
#### Post date: [November 25, 2009, 7:51am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/2 "2009-11-25T07:51:44Z")
They just connect their tool to the battery and it tells them if its good or not.
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### Author:  [@deadbeatrec](https://forums.speedlife.net/u/deadbeatrec)
#### Post date: [November 25, 2009, 7:52am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/3 "2009-11-25T07:52:08Z")
its that simple huh?
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### Author:  [@GermanPSI](https://forums.speedlife.net/u/GermanPSI)
#### Post date: [November 25, 2009, 7:52am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/4 "2009-11-25T07:52:34Z")
i havent heard about that, just plug some radar detector into a cig lighter and see what kinda volts it puts out while running/not running
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### Author:  [@Shady](https://forums.speedlife.net/u/Shady)
#### Post date: [November 25, 2009, 7:53am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/5 "2009-11-25T07:53:26Z")
> [@Hottest Acura Ever?](https://forums.speedlife.net/t/hottest-acura-ever/26330/14):
>
> how can i do this?
>
> i called pepboys and they say they have a scan tool that will run through the whole system. but i find it hard to believe that it will target the alternator specifically.
>
> thoughts?
From in the car all the will be able to tell you is volts…
Theyd have to put a battery/altenator tester hooked up to the battery and put a load o nthe altenator to see if its bad or not
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### Author:  [@deadbeatrec](https://forums.speedlife.net/u/deadbeatrec)
#### Post date: [November 25, 2009, 8:14am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/6 "2009-11-25T08:14:08Z")
just went outside with a multimeter and…
everything off, the new battery reads like 12.37v
car on with lights on and radio blasting, the battery reads 14.18v
i think im good.
thanks for nothing shift.
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### Author:  [@Yetti\_VR](https://forums.speedlife.net/u/Yetti_VR)
#### Post date: [November 25, 2009, 8:29am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/7 "2009-11-25T08:29:01Z")
you did it correctly…
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### Author:  [@DUKE\_LADUKE](https://forums.speedlife.net/u/DUKE_LADUKE)
#### Post date: [November 25, 2009, 8:30am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/8 "2009-11-25T08:30:38Z")
Piece of cake …noob
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### Author:  [@ninety1two40](https://forums.speedlife.net/u/ninety1two40)
#### Post date: [November 25, 2009, 8:31am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/9 "2009-11-25T08:31:41Z")
> [@RANT re: Cops](https://forums.speedlife.net/t/rant-re-cops/26272/102):
>
> just went outside with a multimeter and…
>
> everything off, the new battery reads like 12.37v
>
> car on with lights on and radio blasting, the battery reads 14.18v
>
> i think im good.
>
> thanks for nothing shift.
looks good to me newbcake
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### Author:  [@Shady](https://forums.speedlife.net/u/Shady)
#### Post date: [November 25, 2009, 8:32am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/10 "2009-11-25T08:32:44Z")
> [@RANT re: Cops](https://forums.speedlife.net/t/rant-re-cops/26272/102):
>
> just went outside with a multimeter and…
>
> everything off, the new battery reads like 12.37v
>
> car on with lights on and radio blasting, the battery reads 14.18v
>
> i think im good.
>
> thanks for nothing shift.
That works just fine…
The only thing the pep boys one does is just put a huge load on the altenator to see if it dies under a big load…
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### Author:  [@bennyfizzle](https://forums.speedlife.net/u/bennyfizzle)
#### Post date: [November 25, 2009, 8:36am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/11 "2009-11-25T08:36:25Z")
what are you concerned about, like, what was your reasoning for thinking the alt is bad?
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### Author:  [@Shady](https://forums.speedlife.net/u/Shady)
#### Post date: [November 25, 2009, 8:37am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/12 "2009-11-25T08:37:29Z")
> [@FS: Sabres Playoff Tickets](https://forums.speedlife.net/t/fs-sabres-playoff-tickets/26265/7):
>
> what are you concerned about, like, what was your reasoning for thinking the alt is bad?
His portable blow job on the go killed the battery to fast
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### Author:  [@deadbeatrec](https://forums.speedlife.net/u/deadbeatrec)
#### Post date: [November 25, 2009, 8:43am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/13 "2009-11-25T08:43:28Z")
> [@FS: Sabres Playoff Tickets](https://forums.speedlife.net/t/fs-sabres-playoff-tickets/26265/7):
>
> what are you concerned about, like, what was your reasoning for thinking the alt is bad?
i dont know how long the alternator has been in there. no idea if its been replaced or not. its lookin ratty.
this and…when i got the car it had an optimum battery in it which ANTLS (fucking homo) said was brand new. so…few days later at work it wouldnt start. so i took the battery out, had it tested and it was dead. got a new battery for the cose of $178. starts great but…my concern was that the other battery died because it was running everything without the alternator and thats y it died so quick. so i wanted to make sure the alternator was ok and i wasnt just running on battery power alone.
u seeeeeee???
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### Author:  [@tdi\_logik](https://forums.speedlife.net/u/tdi_logik)
#### Post date: [November 25, 2009, 8:57am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/14 "2009-11-25T08:57:58Z")
strong work guy
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### Author:  [@ReDevil](https://forums.speedlife.net/u/ReDevil)
#### Post date: [November 25, 2009, 9:01am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/15 "2009-11-25T09:01:02Z")
Cant you just have the car running and disconnect the battery? Then the alternator, if good, would allow everything to still work. I know you solved your problem, I am just curious.
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### Author:  [@bennyfizzle](https://forums.speedlife.net/u/bennyfizzle)
#### Post date: [November 25, 2009, 9:18am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/16 "2009-11-25T09:18:23Z")
the bosch/valeo alternators in these cars are not known for failure, no worries unless the charging voltage dies off abruptly.
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### Author:  [@deadbeatrec](https://forums.speedlife.net/u/deadbeatrec)
#### Post date: [November 25, 2009, 9:20am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/17 "2009-11-25T09:20:50Z")
thanks brah
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### Author:  [@Shady](https://forums.speedlife.net/u/Shady)
#### Post date: [November 25, 2009, 9:28am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/18 "2009-11-25T09:28:03Z")
> [@WTB: suit of armor](https://forums.speedlife.net/t/wtb-suit-of-armor/12393/28):
>
> Cant you just have the car running and disconnect the battery? Then the alternator, if good, would allow everything to still work. I know you solved your problem, I am just curious.
No, the battery is what completes the circut. The altenator is simply a device that keeps the battery constantly charged, most altenators dont posses enough power alone to keep “newer” car running.
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### Author:  [@Alpine](https://forums.speedlife.net/u/Alpine)
#### Post date: [November 25, 2009, 9:30am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/19 "2009-11-25T09:30:07Z")
test the output on the alternator using a dmm.
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### Author:  [@Gendy](https://forums.speedlife.net/u/Gendy)
#### Post date: [November 25, 2009, 10:49am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/20 "2009-11-25T10:49:10Z")
I had alternator problems once. Went to sears and they sold me some new tires. They didn’t work well offroading though. PRobably won’t buy those tires again.
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