2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

charging woes...

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Old Nov 9, 2007 | 09:09 PM
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charging woes...

hey guys noticed my charging system was only charging like 12.5 volts...looked for loose connection and noticed when i unhooked the plug from the back it went up to 13.8 volts???
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Old Nov 9, 2007 | 09:26 PM
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Originally Posted by re-rx7
hey guys noticed my charging system was only charging like 12.5 volts...looked for loose connection and noticed when i unhooked the plug from the back it went up to 13.8 volts???

I'm not sure that's a question. At least I don't even know how to answer what's before the question marks.
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Old Nov 9, 2007 | 09:28 PM
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What is the function of this plug???
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Old Nov 9, 2007 | 10:31 PM
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Which plug? On the back of the Alternator? On the battery? On the engine? On the wiring harness?

Do you have a picture of what you're refering to?
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Old Nov 9, 2007 | 10:34 PM
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On the back of the alternator. The one that plgus into the back of the alternator.
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Old Nov 10, 2007 | 11:23 AM
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Seems like it might be a bad voltage regulator. Solution = new alternator. Pull your alternator and battery, bring to any automotive store and have them test both (free). But I wouldn't buy a new alternator from them. Ask a mechanic for a good alternator shop. But if you can't/don't want to search for a good alternator shop, buy an alternator from the automotive store and make sure you save the warranty info. Maybe the auto-store alternator will last a long time, maybe it won't. It's a real gamble.

The FC's charging system consists of an alternator with a built in voltage regulator, a battery, and wires. So there's practically nothing that can go wrong besides a bad alt, bad battery, a short or a blown fuse.
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Old Nov 10, 2007 | 02:12 PM
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That all i needed to knnow!!
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Old Nov 10, 2007 | 02:46 PM
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Sorry didn't teply earlier, as I saw there was 8 repiles, but when I opened the thread I see that two of them are bumps. If the bumps (which are now deleted) were not there, the thread would have probably been looked at earlier, by one of the gurus.


The plug on the back of the alt provides signal out for alternator failure and a reference voltage in, to tell the regulator to turn on or off.

If you have installed the wrong series alt, then or swaped to a different series alt than the engine's wiring, the regualtor will not turn on correctly. If it is the correct alt for the harness and you are still not getting at least 13.5 volts, then the alt is probably bad.

As a note, if you replace the alt stay away from Rebuilt Alternators like you find at the cheap auto parts stores like Auto Zone. You want a remanufactured alternator. The differnece being that a rebuilt alt, just has the broken parts replaced and then cleaned, while a remanufactured alt, has any part that wears replaced.
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