Alternator/Electrical problems...

[DoctorRobert]

Okay, I have a problem with me car that's really starting to give me a headache, and I could really use some help.

For starters, it is an all stock '93 240 'vert.

About a week ago I was going somewhere with the air conditioner in the car on, when I stopped and then tried to start the car again, the battery was dead. I got it jumped off, and drove it home, but when I tried to start it again, the battery was dead. After that I didn't run the air, and the car seemed to run fine. I just needed it to last until I could get the alternator replaced. Then this past Saturday, I was leaving a Fourth of July celebration at Ft Benning when my radio cut off and my lights went dim. I figured the alternator had gone out on me and I was just running on battery, so I drove it the about twenty miles home where I parked it and found the battery to be, as I figured it would be, completely drained.

I charged the battery and drove it the thirty mile trip out to my step-Dad's where I was going to have it fixed. Ran fine. We replaced the alternator, and I drove it back to town. Everything seemed fine.

Then this morning I get in the car to go to work and when I start the car the BRAKE light is on and the BATTERY lights are on. I drive it the mile or so to work and it runs fine. After work I take it across town to the Auto Zone where I bought the alternator from. They test the car and battery while it's running and tell me that the battery is going bad (it's new) and it's not getting any charge back from the alternator, and that I need to bring it in and have it bench tested. On the way home, the brake light goes off, and this almost electrical buzzing sound comes from under the dash board, when I press down the gas, the light goes off and then comes on again. Both times accomponied by the buzzing sound. When I got home I looked under the dash and revved the car, and it seems that the sound is coming from a green box that is marked "SHIFT LOCK CONT - ASSY."

Now, I'm lost... any ideas?

[KA24M90]

In any case where the alternator is not charging the battery, it should be bench tested. When tested on the car there are to many variables that are seen by the equipment to actually tell weather it is a problem with the alternator itself or possibly in the wiring.

As for the buzzing noise, same thing happened to me. Auto 89 240sx (being converted to manual), bad alt bought one from the wife at Auto Zone, installed it, heater hose starts pissin all over it a week later, and I start getting upwards of 16-17 volts. Brake light on and everything.

Take it to more than one part store, some one is bound to test it wrong.Good luck man.

[DoctorRobert]

So... you're basically saying it probably is a bad alternator? From the buzzing and all.

I had it tested at two other part stores, they both said it was good and putting out 13 amps. The battery hasn't gotten weak since I replaced it either... just the darn buzzing and brake light. Also, the buzzing stops when the car hits about 2000 RPMs, but once it drops below that it starts again. The brake light also gets brighter when it hits 2000 rpms.

So, do I just need to get the alternator out as soon as possible and take it to Auto Zone and get it replaced? Or is there anything else it might be?

[DoctorRobert]

Okay... I was wrong about where the buzzing is coming from. I unplugged the green box and all the buzzing and whatnot was still there, so that's obviously not what's making the noise. I also had it tested again at auto zone and this time they said it was fine. This is driving me crazy. And the problem is I can't take it out by myself. Is it simply the alternator?

[Vegascorbin]

...I had it tested at two other part stores, they both said it was good and putting out 13 amps....

13 amps out of an altinator is not good. it should be putting out over 50 amps. 13 Volts is low also. it shoud be putting out 14 or more.

Take both the Battery and ALtinator to some shops/stores that can test them and see what they say. Also when you install the altinator be sure the bet is tight. And ensure the battery cables are clean and tight.

I think one or both are bad. Let us know what you find.

[northstar ninja]

make sure you didnt blow your alternator fuse taking the alternator out. I know that sounds stupid but Ive done it. I thought I had the battery disconnected and the hot wore grounded out against the frame and blew the alternator fuse.

[slinds14sr20]

If your brake light and battery light are on, the system is charging at either above 15 volts or below 10 volts. More likely your alternator.

[Drifter-N-Makes]

just saw this thread i had a similar issue with a 91 sentra. my problem was on the positive cable to the battery theirs a fuseable link and some one tried replacing it with a inline fuse and it did nothing but cause issues i replaced it with the proper fuseable link and it solved the problem all the buzzing stopped and no more charging problems. hope this helps better late than never.