# testing alternator while in car **URL:** \ **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:** 11\ **Page:** 2
**Author:** ![bennyfizzle](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/bennyfizzle/32/6291_2.png) [@bennyfizzle](https://forums.speedlife.net/u/bennyfizzle)\ **Post date:** [November 25, 2009, 11:03am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/21 "2009-11-25T11:03:43Z")
Thanks PJB :rofl ---
**Author:** ![94Gt5.0](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/94gt5.0/32/6377_2.png) [@94Gt5.0](https://forums.speedlife.net/u/94Gt5.0)\ **Post date:** [November 25, 2009, 3:04pm UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/22 "2009-11-25T15:04:58Z")
Lick the alternator, get boner. /Thread ---
**Author:** ![88slowmarro](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/88slowmarro/32/6339_2.png) [@88slowmarro](https://forums.speedlife.net/u/88slowmarro)\ **Post date:** [November 25, 2009, 4:59pm UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/23 "2009-11-25T16:59:57Z")
to properly test a alt ya load it with the car runnin and see how many amps it can supply at a given load amount or with a dmm turn on all accesories and test that way .emmanual if ya need to call me fri or sat and ill run it at the shop i have a load tester and analizer ---
**Author:** ![offroadzj](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/offroadzj/32/6428_2.png) [@offroadzj](https://forums.speedlife.net/u/offroadzj)\ **Post date:** [November 26, 2009, 5:42am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/24 "2009-11-26T05:42:46Z")
Yes the disconnecting the battery trick does work (possibly not on all cars). I have done it on my jeep and my dodge to check it. ONly disconnect the positive, not the ground from the battery and keep the alt. positive connected to the car. If it continues to run your alt is good. If it dies however, it does not necessarily mean the alt is bad as it could still be a bad ground/connection, etc. ---
**Author:** ![TurboTravis](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/turbotravis/32/6406_2.png) [@TurboTravis](https://forums.speedlife.net/u/TurboTravis)\ **Post date:** [November 26, 2009, 5:45am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/25 "2009-11-26T05:45:13Z")
E, your alternator is fine, if you want to test it more, turn on all available accessories (defrost, stereo, lights, etc) and retest voltage. As long as it’s suffecient, like high 13s, low 14s, whatever, you are good to go. Don’t listen to anyone telling you to disconnect it, no need to run it thru scanners and shit, etc. ---
**Author:** ![offroadzj](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/offroadzj/32/6428_2.png) [@offroadzj](https://forums.speedlife.net/u/offroadzj)\ **Post date:** [November 26, 2009, 9:22am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/26 "2009-11-26T09:22:09Z")
i agree that there is no need. If he is showing 14+v then it is fine. I was just stating that it can be done. ---
**Author:** ![88slowmarro](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/88slowmarro/32/6339_2.png) [@88slowmarro](https://forums.speedlife.net/u/88slowmarro)\ **Post date:** [November 26, 2009, 9:33am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/27 "2009-11-26T09:33:01Z")
> [@Where did my voicemail go (VZW)?](https://forums.speedlife.net/t/where-did-my-voicemail-go-vzw/26343/12): > > Yes the disconnecting the battery trick does work (possibly not on all cars). I have done it on my jeep and my dodge to check it. ONly disconnect the positive, not the ground from the battery and keep the alt. positive connected to the car. If it continues to run your alt is good. If it dies however, it does not necessarily mean the alt is bad as it could still be a bad ground/connection, etc. great way to blow out b.c.m,s and other modules by disconecting the battery while running like i said before your testing with a dmm and gettin 14 and change you should be fine next though run all your acces while doin it so its under load ---
**Author:** ![offroadzj](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/offroadzj/32/6428_2.png) [@offroadzj](https://forums.speedlife.net/u/offroadzj)\ **Post date:** [November 26, 2009, 11:37pm UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/28 "2009-11-26T23:37:11Z")
How are you damaging equipment? Your ground does not change and as long as you do not disconnect the power from the alt. to the vehicle you will not lose power or get a spike. A battery is in simply to store power for when the vehicle isnt running. Otherwise while the vehicle is running, the power is coming straight from the alt. anyways. Edit: Yes, if you leave it disconnected for an extended period, then yes the fluctuation in voltage could damage equipment. But if you simply disconnect it for a few seconds to see if the vehicle stays running I see no danger. ---
**Author:** ![ninety1two40](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/ninety1two40/32/6332_2.png) [@ninety1two40](https://forums.speedlife.net/u/ninety1two40)\ **Post date:** [November 27, 2009, 10:29am UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/29 "2009-11-27T10:29:21Z")
Removing the battery while running might damage the alternator, depends on the electrical load. ---
**Author:** ![offroadzj](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/offroadzj/32/6428_2.png) [@offroadzj](https://forums.speedlife.net/u/offroadzj)\ **Post date:** [November 27, 2009, 2:12pm UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/30 "2009-11-27T14:12:38Z")
if you have all accessories on then it could be unstable enough to cause damage, but it would be a one in a million shitty day… lol ---
**Author:** ![deadbeatrec](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/deadbeatrec/32/6401_2.png) [@deadbeatrec](https://forums.speedlife.net/u/deadbeatrec)\ **Post date:** [November 27, 2009, 3:13pm UTC](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617/31 "2009-11-27T15:13:38Z")
im def not disconnecting the battery. i have heard many horror stories about this fring the ECU. [Previous page](https://forums.speedlife.net/t/testing-alternator-while-in-car/248617.md?page=1)