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Old 05-02-2014, 08:30 AM   #1
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Alternator Output

Is this low or normal?

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Old 05-02-2014, 08:56 AM   #2
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if your gauge is correct thats not normal, but if your not having starting issues then the gauge is probably broken somewhere between the gauge itself and the sending unit.

get a multimeter and check the voltage at the battery, should be around 13.8 to 14.2 volts

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Old 05-02-2014, 10:00 AM   #3
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It does labor during starting. Sounds like I need a battery and an alternator.
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Old 05-02-2014, 11:33 AM   #4
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With the Jeep running, the voltage coming off the alternator should read 13.8-14.2, with the Jeep off the voltage at the battery should be 11.8-12.

A quick test to see if the alternator is working, start the Jeep, and then with it running, take the positive terminal off the battery. If the Jeep dies, or starts running rough, the alternator is in need of replacement.
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Old 05-02-2014, 11:37 AM   #5
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If that is with the engine running, it is not normal.

Mine is at 14 volts which is normal.

The battery is nominally 12.6 volts with the engine off.

If you have a multimeter, you can check at the battery terminals.

But if your alternator is shot it will read much less.
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Old 05-02-2014, 12:30 PM   #6
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Quote:
Originally Posted by 0iii0forlife View Post
with the jeep running, the voltage coming off the alternator should read 13.8-14.2, with the jeep off the voltage at the battery should be 11.8-12.

A quick test to see if the alternator is working, start the jeep, and then with it running, take the positive terminal off the battery. If the jeep dies, or starts running rough, the alternator is in need of replacement.
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Old 05-02-2014, 12:52 PM   #7
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Not a good idea to remove a battery cable when running on a computer controlled vehicle. You run the possibility of sending a voltage spike to the computer which is the primary reason ECMs die. Its best to check battery voltage first with it shut off then after while its running. It should be 13.8-14.2. A fully charged battery should read 12-13 volt range. Battery load testers are available for about $20.00 at HF it should hold a load @ 10+ volts for 10 seconds if not battery is probably bad.
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Old 05-02-2014, 04:19 PM   #8
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Not a good idea to remove a battery cable when running on a computer controlled vehicle. You run the possibility of sending a voltage spike to the computer which is the primary reason ECMs die. Its best to check battery voltage first with it shut off then after while its running. It should be 13.8-14.2. A fully charged battery should read 12-13 volt range. Battery load testers are available for about $20.00 at HF it should hold a load @ 10+ volts for 10 seconds if not battery is probably bad.
That's very true Mow, my bad. I always forget about those damn ECM's being picky about voltage spikes. I eliminated all the computer controlled everything on mine, and forget about it when I am giving info.

Sorry for my post to the OP, do it the way that Mowrangler stated.
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Old 05-03-2014, 12:57 PM   #9
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Originally Posted by Rlhoffman View Post
It does labor during starting. Sounds like I need a battery and an alternator.
have autozone/ napa or o'rileys test both of them

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