Alternator Question -
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post #1 of 4 Old 05-25-2013, 10:40 AM Thread Starter
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1984 CJ7 
Join Date: Jan 2013
Location: Stafford
Posts: 11
Alternator Question

Hi everyone,

So a little back story before I get to my questions. I was driving the jeep last night and stopped for gas. When I tried to get going again it wouldn't turn over. I was able to bump start it (by myself, in an HEB parking lot...) and get it back home, but it wasn't able to start from the battery anymore. I figured it was the battery, so I went to autozone and picked up a new one. When I got that it, the voltage meter was only saying it was at about 11-12 volts when I was driving, so when I returned the core battery they check my alternator and they said that it was only putting out about 12v, when it should really be putting out about 13-14v. They recommended I replace the alternator too.

I unfortunately am just getting started in the world of do-it-yourself repairs, and I was wondering if anyone could weigh in on whether that would be the right approach, or if there is anything else I should check before I just start throwing money at it and replacing entire components.


BTW: It's an 84 CJ7 inline 6 4.2

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post #2 of 4 Old 05-25-2013, 11:26 AM
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1974 CJ5 
Join Date: Oct 2011
Location: Huntsville
Posts: 696
They are correct, your alternator should put out between 13 and 14v when the engine is running. Also, your alternator is internally regulated, meaning there is no other little part that could be causing the problems. That being said, if you really want to be sure, you can take a volt meter to the hot post on the back of the alternator while the engine is running and confirm that there is only 12v there. If this is the case, you need a new alternator.

If, for some incredibly weird reason, you have 13-14v at the alternator, you need to start chasing wires and look for a broken wire or a bad connection.

Also, be forwarned that if you get an arm/sleeve/ponytail/anything caught up in the fan or the belt while the engine is running, you are going in there with it. Just watch your fingers and stay away from moving parts.
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post #3 of 4 Old 05-25-2013, 12:56 PM Thread Starter
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1984 CJ7 
Join Date: Jan 2013
Location: Stafford
Posts: 11
Thanks for the reply. I went ahead and just took the whole alternator in to Autozone and got a new one. They hooked my old one up the machine and it started making a god awful sound. When he came back he told me my alternator started coming apart while he was testing it. So it failed.

Thanks for the tip. I have everything unhooked as of now, but I will definitely keep all my parts out of the way!

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post #4 of 4 Old 05-26-2013, 12:36 PM
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1979 CJ7 
Join Date: Dec 2008
Location: Las Vegas
Posts: 1,046
It's worth the extra 10 minutes to make up a new set of wires for the alternator. You can get the new 'GM' pigtail for the alternator at any parts store (on the shelf near the fuses) and go from there. Just a little insurance. I just did mine when I upgraded my alternator because the old wiring was burnt.

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