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-   -   Voltage/alt issues (http://www.wranglerforum.com/f282/voltage-alt-issues-169915.html)

NC10735285 06-28-2012 09:52 AM

Voltage/alt issues
 
How do I test the alternator to make sure it's working properly

Wattapunk 06-28-2012 10:34 AM

Check your battery voltage with engine off/on. Should be 1-2 volts more with engine running(approx.13.5-14.5v). Another crude way of checking it would be disconnect the battery negative cable with engine running. Bad alternator would kill the engine.

dusman 06-28-2012 10:38 AM

http://www.youtube.com/watch?v=Bzz7P3qNHcE

Jerry Bransford 06-28-2012 10:51 AM

Quote:

Originally Posted by Wattapunk (Post 2523751)
Another crude way of checking it would be disconnect the battery negative cable with engine running. Bad alternator would kill the engine.

That isn't true with the TJ's alternator which requires 12 volts from the battery for it to work. Disconnecting the battery will always kill the engine on most modern engines, not many vehicles still use the type of alternator that can run without a battery. GM is one except and there are others but...

In fact, if you have a completely dead battery and jump start any modern Jeep's engine, the engine will die again after you disconnect the jump start battery. Same thing is true with my daily-driver Toyota whose battery gives me fits.

Wattapunk 06-28-2012 10:59 AM

Didn't know that. Thanks for the info.

NC10735285 06-28-2012 12:04 PM

Thanks for ALL the great information -you guys rock! (no pun intended - ok maybe I did)


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