Help battery over charge

pokeyl

After picking up the new alternator, I did not want to change it as the GTM supercharger kit makes it an all day job. So before I started I looked for other causes...

Looking at the wiring "Charging System" (CHR-15) I inspectied the fuses, found one blown. I have a FSM and it never even talks about a fuse on the S termanal. Only if you are missing voltage, repair wiring. Nissan did not make this manual easy to navigate.

The other part of troulbleshooting this was the "Brake Lite" was on as well. I also looked at the wiring for that. It is just the switch and the LED. Not connected to the other LED in any wey that you can see in the wiring. After that you have to be getting power to the LED to light both of them from some other path.

I still can't find that path but if I could see the inside of the LED's waring lites I think you would find the two on the same board without any power isolation. Power is sitting on the brake looking for a ground and the battery is the same. The groung came from the voltage regulator when the power was not supplied to termial "S"???

We will never know, but if you wasnted to see what I did, just pull the 10A fuse. I hope this helps other someday. I have to take the alternator back now, full refund from Carquest.

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It's not my fault I'm old, I was born a very long time ago!

pokeyl

Text from manual

S TERMINAL CIRCUIT
Description INFOID:0000000004457529
The output voltage of the alternator is controlled by the IC voltage regulator at the “S” terminal detecting the
input voltage.

The “S” terminal circuit detects the battery voltage to adjust the alternator output voltage with the IC voltage
regulator.

Diagnosis Procedure INFOID:0000000004457530

1.CHECK “S” TERMINAL CONNECTION
1. Turn ignition switch OFF.
2. Check if “S” terminal is clean and tight.
Is the inspection result normal?
YES >> GO TO 2.
NO >> Repair “S” terminal connection. Confirm repair by performing complete
Starting/Charging system
test. Refer to Technical Service Bulletin.

2.CHECK “S” TERMINAL CIRCUIT
Check voltage between alternator harness connector and ground.
Is the inspection result normal?
YES >> Refer to CHG-3, "Work Flow".
NO >> Check harness for open between alternator and fuse.

Do you see the words "check fuse" in here?

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It's not my fault I'm old, I was born a very long time ago!

SouthArk370Z

Wow! Thanks for such a detailed explanation.

The FSM usually does a pretty good job but, in this case, it's not very clear what's going on. And I saw no mention of the fuse (#32) in the troubleshooting guide.

I didn't see anything in the CHG section of the 2009 FSM that would indicate that the brake light will come on in your situation. It might show up in one of the braking sections.

Thanks again for sharing your troubleshooting process.

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roy'sz

brake light is normal when indicating a charging failure. This happened to my wife's Altima last month. Some worker thought that they were going to take me for 500 bucks at this tire shop in riverside by loosening the charging wire to my wifes alternator and my wife kept getting a intermittent failure. i.e. brake light and engine light. Now this may be slightly different because the voltage is obvious but atleast you know now why the brake light.

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