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Discussion Starter · #1 ·
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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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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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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Discussion Starter · #4 · (Edited)
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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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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