# Is my 1995 Nissan Maxima's alternator bad?



## Mark_42 (Aug 2, 2018)

I have a 1995 Nissan Maxima GLE. The car has only 50000 miles on it.


A few days ago, I came into the garage, and saw that the trunk of the car was open and that the internal light in the trunk was off. I had not opened the trunk. The trunk had opened by itself. 

I did not know how long the trunk had been open. 

I tried to start the car, but the car would not start. The engine did not make any noise at all. There was complete silence.


I was able to jump start the car. I drove the car for 15-20 minutes to recharge the battery.

On the next day, I tried to start the car. Once again, the car would not start. The engine did not make any noise at all. There was complete silence.

I thought that the battery had lost its ability to maintain a charge. (I had bought the battery only 28 months earlier.) 


Today, I jump started the car, drove around for about 30 minutes to recharge the battery, and took the car to a Nissan dealership. The dealership added some more charge to the battery, and then ran a battery test. The battery test showed that the battery was good. 

The dealership subsequently tested the entire electrical system of the car. According to the dealership, the test showed that the alternator was bad. I was told that a new alternator would cost over $700. I said that I would shop around, and took the car home.


I'm trying to figure out exactly how a bad alternator would cause the problems that my car has been experiencing. $700 is a lot of money, and I'm very skeptical of the idea that the alternator is bad.

On the day on which I found the open trunk, I jump started the car and drove for 15-20 minutes to recharge the battery. On the next day, the car would not start. How is a bad alternator responsible for this? Did the bad alternator cause the battery to lose the 15-20 minutes of charge that I had given to the battery on the previous day?


Any help would be appreciated. Thank you.


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## rogoman (Dec 16, 2004)

First thing to do is test the alternator. A properly working charging system puts out about 13.2 to 15.0 volts. A battery should have a static charge of 12.2-12.6 volts. If a battery is not good, the charging system may not be able to charge properly. If a vehicle is not charging properly and the battery is good, the first thing to do is to turn the ignition switch to the "ON" position *without starting the engine* and make sure the charging system warning light is operating. If the bulb is burnt out, the charging system will not charge. If the bulb is OK but still does not illuminate, the circuit must be tested. If the warning lamp does illuminate, then the next thing to check is to make sure the circuit between the battery positive post (+), or fusible link, to the connection in back of the alternator is good. On Nissans, this should be a thick (approx. 10 gauge) white wire to the "BAT" post on the back of the alternator. With the negative cable (-) disconnected from the battery, measure the resistance between the "BAT" post on the back of the alternator and the battery positive (+) post; the resistance should not be greater then 0.2 Ohms. It's not uncommon for this wire to get corroded and burn up, creating resistance in the circuit. So, before assuming an alternator is bad, make sure this circuit is good and battery voltage is getting to the alternator. It's also important to make sure the alternator belt is tight and not slipping and the battery connections are clean and tight.

Assuming the charging system voltage is OK and the battery is good, the next thing to do would be to have a parasitic draw test performed; there should not be more than a 50 milliamp draw on the system with the ignition switch in the "OFF" position. If there is a higher draw, you need to do some testing to find out where the draw is coming from. Remove fuses one at a time until the draw goes away or falls into acceptable range.

If you plan to do a parasitic draw test, make sure all accessories inside the car are shut off; this includes any courtesy lights such as the overhead lights. If the hood has an opening security sensor, it must be disabled. All the doors and trunk must be closed; if you need to have the driver's door open, put something against the door button to keep it pressed in order to break the electrical circuit. There should not be more than a 50 milliamp draw on the system with the ignition switch in the "OFF" position. The reason being is the ECU is always on in sleep mode which accounts for the very small draw.


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## VStar650CL (Nov 12, 2020)

Mark_42 said:


> How is a bad alternator responsible for this? Did the bad alternator cause the battery to lose the 15-20 minutes of charge that I had given to the battery on the previous day?


It's very common for a melted rectifier inside the alternator to cause a key-off current draw. Usually the draw from a bad diode is at least 2 amps and can go as high as 7-8 amps, so it will drag a battery down fast.


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## Mark_42 (Aug 2, 2018)

VStar650CL said:


> It's very common for a melted rectifier inside the alternator to cause a key-off current draw. Usually the draw from a bad diode is at least 2 amps and can go as high as 7-8 amps, so it will drag a battery down fast.


I took the car to the dealership and then brought the car back home, on March 6, 2021.

After I brought the car back home, I did not attempt to start the car again until March 12. Between March 6 and March 12, from time to time, I successfully opened the trunk (electronically, from inside the car) and successfully turned the headlights on and off.

When I attempted to start the car on March 12, the car started just fine.

So, I don't think that there is any key-off current draw from the battery.


I think that I'm going to send an email to the technical adviser who waited on me at the dealership. I'm going to ask him which test(s) the dealership ran on the car's electrical system, and I'm going to ask him for written documentation of the test results. The poster named rogoman described a bunch of tests in detail, and I'm going to try to find out which of these tests were run on my car.


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## VStar650CL (Nov 12, 2020)

Mark_42 said:


> So, I don't think that there is any key-off current draw from the battery.
> 
> I think that I'm going to send an email to the technical adviser who waited on me at the dealership. I'm going to ask him which test(s) the dealership ran on the car's electrical system, and I'm going to ask him for written documentation of the test results. The poster named rogoman described a bunch of tests in detail, and I'm going to try to find out which of these tests were run on my car.


You're right, that certainly excludes a draw issue. The battery testers used by Nissan dealers have an "all in one" system test function that checks starter and alternator performance in addition to battery CCA, and can detect bad alt diodes. That's what they should have used on your car. If so, there should be a printed test strip attached to the hardcopy of your Repair Order in their files. If they say they don't have one then you can be pretty sure they didn't test properly.


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## Maximat (11 mo ago)

Old thread resurrected.

I bought a 95 Maxima from a guy. Turns out it had a rebuilt title. Not sure what all was involved in the rebuild.
The sunroof drains were defective and it leaked profusely...a moderate rain would leave an inch of water on the floor..then, the car sat forever... there was moss growing on the carpet.. real, green moss! I am leery that all that moisture, for extended period of time, inside the cabin of the car might cause electric problems...

Anyhow, dried things out, had my mechanic fix a few things, like the rear valve cover gasket...brake pads... and started driving it.

Well, it has an intermittent miss and some 02 sensor codes.

The alternator didn't seem to keep the battery charged. I charged the battery out of the car overnight, and took it to the parts store and had them test it. It is one year old.. tested good.

I had checked the 2 fuses in the charging circuit, and they were both good.

After an all night stint on the charger, drive it for 15 minutes and the battery light would illuminate, push your luck and drive it with the lights or heater on... it's liable to die and strand me after extended use.

It's amazing how much current an automobile draws... it can draw a big battery down enough just driving it around that by the time it's too late, step on the brakes and just the current drawn by the brake lights would lower the battery voltage enough that the ignition wouldn't operate and it would die!

So I got on "PartsGeek" and ordered a Remy reman. (p/n13402) Hitachi/Nissan logo'd alternator. I got a midrange priced one...$103, with a $71 core charge.

Then, I did something I'd bet most people don't do~ when I got it, I took it right out of the box and took it to the Orielly auto place and had them put it on their alternator tester. Amazingly, it failed the test. They tried twice.

I left there and went to the NAPA parts store. Employee brought it back and said "our machine is having problems, but it says it failed the test.

I'm setting there thinking that it's a good thing I had this tested, cause if I'd have it installed and it's bad, I'm out money for the mechanics costs of doing it, and the time waiting for a replacement.

But, I have an alternator testing machine of my own, so I took it to my shop and put it on... that s.o.b. put out over a hundred amps... pegged the 75 amp meter on my machine.

Not sure what is up with the parts store machines.

You always read about someone having charging problems and inevitably, they'll replace the alternator and still have the problem....and they're not sure if the new alternator is actually good or bad. I was going to head that problem off at the pass. Testing the brand new alt. removes all doubt that it's the new part.

So, I took the car to the shop today. I told the guy "when you get the old one off, call me and let me go test it to be sure it's really bad (they don't have a stand alone testing machine), so I am not just throwing away money throwing parts at it. And, since the car was rebuilt at some point, I want to be doubly sure that it's not a wiring issue.

He agreed.

Called me, I came and got it... tested it at my shop, and it was defective. I called them and told them to put the new one on. Called me back later after it was done, and it's working like it's supposed to, now.

Took the old one apart on my bench... the armature slip rings were worn waaayyyy down- the brushes had worn uneven grooves in the slip ring surfaces... and the brushes were stuck in the holder- and worn a little more than halfway down.

I got the brushes loose and moving in their holders and reassembled it... still won't work, so I just put it back together and am sending it as a core back to PartGeek.

I didn't bother to check the armature for continuity... but something like that rarely ever goes bad. They're tough. About the only thing to go bad is the diode set or the regulator. If one diode goes bad, it will still produce some current, but not efficiently.

Since the bad slip rings made the armature unusable, I decided to send it back. If it had been good, and the regulator or diode set was bad, I'd have kept it and bought parts to fix it and sent PartsGeek some other alternator.

I contacted them early in the process (when I thought I might just keep the old one to have a spare...and send them an impostor) and asked a person on their "chat" link "do I have to send an identical core alternator to the one I bought, or does it just have to be an "alternator", one that's "similar". He replied "similar is fine".

Hell, I'd have sent them a 1962 Delco external regulated p.o.s., lol!


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