# Charging System Problems - '96 Sentra GA16DE



## jstluise (Mar 20, 2009)

Well I've been having some sporadic issues with this car. Sometimes the problem happens and sometimes it doesn't. Usually seems to happen when the system is loaded (e.g. at night with headlights on, etc).

So when I am driving, everything seems fine but then I'll start loosing power to all my accessories...my headlights will dim, dashlights will dim, etc...as if the alternator goes out and I am driving off my battery only. One time it got so bad everything was practically off except the engine (even the radio went off because of lack of voltage). I had to get jumped that time because my battery was drained after I shut the car off. After I got jumped everything was fine.

So, sometimes it happens for a short period of time then acts fine. I took it down to the autoparts store to check the charging system on the car with their portable testing unit and everything checked out fine. Battery was strong (full CCA) and alternator was putting out voltage....

Now I have been carrying around my multimeter with me so I can check the voltage myself when it starts acting up. Last night I noticed my dash lights were dimmer than normal. I pulled over and checked my voltage (with the car running)...~11.9 Volts, didn't seem right (since it was above 14V when I took it to get checked). After I got home, I went to check it again after a little while. Then it was at over 14V! Note: both tests I checked the voltage at the battery AND the alternator, both were the same.

I am thinking something is wrong with the alternator (maybe voltage regulator)...only charging sometimes. BUT, I want to make sure there isn't anything else I can test for before I go pulling the alternator out. I have already cleaned all my connections (battery, engine ground, alternator connections) and they are spotless.

The alternator is less than a year old (replaced with a remanufacted), so I have a lifetime warranty on it. Problem is, if I know its the alternator, they won't replace it unless it tests bad in the autoparts testing machine. So there would be a chance of me pulling it and it testing fine. I don't think they would give me a new one based on my word.

Any advice or recommendations would be very helpful.

Thanks


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## Jdoggsc (Dec 25, 2007)

i can't really imagine this would be causing those problems, but it might be worth your time to check your fusebox too. the one under the steering column, and the one beside the battery.

As far as your accessories going out, that's very indicative of bad alternator. You're driving only on battery power, so when the battery dies, so does everything else. are the brake and battery idiot lights on the dash turning on? Generally that'll happen when your alternator's kicked the bucket. 

Unfortunately, the tests at autozone aren't foolproof, and will often say an alternator is good when it's in fact bad. I don't know the reasons behind that like a lot of other people on this forum do, but it's true. The sucky thing is that if their equipment says your alternator's good and it's actually bad, then you'll have to pay 150 to find out. if it's the problem, voila--problem solved. it's it's not the problem, you can't take it back---but if you get it from autozone, there's a lifetime warranty, so you'll never have to buy another alternator again..they'll just keep replacing them for free.

anyway, let us know what you find out, and what you end up doing. If you find any broken fuses, which ones?


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## jstluise (Mar 20, 2009)

It happened again tonight, so I did a little more trouble shooting. I went on a short drive when it happened, so when I got home I checked the voltages...they were low like there wasn't an output at the alternator.

I shut off the car and waited a half hour and then started it back up. Voltage output was back up to around 14.8V...normal.

I noticed that if I unplug the connector into the alternator (2 wires), the output from the alternator would be shut off. So, from that it can either the alternator that is causing problems or something in the car's wiring...something with the input of plug is going wrong.

Can someone explain the purpose of the 2-wire plug going into the alternator? Does it control the output of the alternator (depending on the load)? If something is wrong with it then that would explain my problem. I am just unsure exactly how the alternator is controlled.

That way when the problem occurs again, I can check that plug to see that is supplying a signal or not...


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## jstluise (Mar 20, 2009)

Jdoggsc said:


> i can't really imagine this would be causing those problems, but it might be worth your time to check your fusebox too. the one under the steering column, and the one beside the battery.
> 
> As far as your accessories going out, that's very indicative of bad alternator. You're driving only on battery power, so when the battery dies, so does everything else. are the brake and battery idiot lights on the dash turning on? Generally that'll happen when your alternator's kicked the bucket.
> 
> ...


Thanks for the reply. Yeah when this problem first started happening my first thought was the alternator. But just that fact it happens sometimes and not others frustrates me because I can't diagnose it easily.

One thing that is odd is the idiot lights do not come on at all...and these lights did come on before when the alternator failed. The first time the alternator failed (the original alt), the lights were one. The first reman I installed lasted a little while before it went on the fritz....and that time the idoit lights were an indication it was going bad. I had that one replaced under the lifetime warranty (through schucks) and now I am on the current one. So now I am scratching my head because those idiot lights are not coming on...crap!

I will check the fuses, but I don't expect to find anything out...mainly because the problem isn't always there. But I could be wrong!

You are right about the bench testing and that's the main reason I want to be sure its that before I go through the hassle of pulling it out.

That's just weird the idiot lights aren't coming on when they have in pass. Can the alt fail w/o triggering the lights? I woudn't think so.


EDIT: So I tracked down a FSM with the wiring diagram and a troubleshooting inspection table. So now I know what the two wires do that plug into the alternator. It seems an easy test to do is to unplug the two wires from the alternator and ground one of them (harness side)...the behavior of the warning lamp will tell me if the regulator is bad and need replacing. 

I will try this tomorrow and give an update.


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## jstluise (Mar 20, 2009)

Update: Problem is fixed...new alternator.

So I ran through the diagnostic the FSM had and it helped to determine something was wrong with the regulator. The FSM was very helpful and it gave me an idea how the system works.

When you turn your key ON (before starting), your charge dummy light comes on because the alternator is grounding that circuit. As soon as the alternator is supplying voltage, the alternator breaks that circuit and this is why the charge light goes off when your car starts up. So in my case, which I didn't even notice, when I turn the key ON (this is after the problem acts up), my charge light is off, though it should be on. This is an indication right away something is wrong with the regulator (granted the charge light circuit is functioning correctly).

But, when the alternator was acting normal, so did the charge light. This was my concern with having it bench tested at Schucks.

Well there wasn't much I could do. I pulled off the alternator and took it into Schucks. They tested it and it FAILED! What a relief! Got the replacement from my warranty and I am back up and running.

One thing I did notice...on the new alternator (reman), there is a big orange sticker that says "Alternator cannot be tested outside of vehicle". This was on the previous reman I got too. Anyone know what this means? I'm just curious. Seems the shop doesn't care because they tested it, unless they don't know what they are doing. Hmmm I dunno.

Anyways, just wanted to post an update.


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