[Event_Horizon]

Hey guys, I'm new here and new to cars in general. I recently bought a '93 Altima GXE and had no problems with it for a few weeks. Then last week a buzzing noise started coming from the floor of the passenger seat. It went away after a minute or so. But now the buzzing noise is back and it doesn't seem to want to go away. I have traced the buzzing noise to a small metal box mounted on the right side of passenger foot area. It was behind some paneling that was easy to remove. I have a picture of the box here:
http://img299.imageshack.us/img299/6871/boxsa2.jpg

When the engine is started while the parking brake is on, the buzzing starts as soon as the parking brake is released. After that, it will not stop if the parking brake is engaged again.

When the parking brake is off, the buzzing starts as soon as the engine is started, and will not stop if the parking brake is engaged.

The buzzing stops when I turn the headlights fully on but returns when the headlights are turned off again.

The buzzing stops whenever the engine is not running.

I have no idea what the small box is or why it is buzzing. There are however quite a few wires running into the box, which leads me to believe that it is important.
I have also included an audio clip of the buzzing noise here:
Download Dh sdh - Free Music Hosting at Supload.com - JAZGX9OX0LFG

Anybody have an idea what this thing is or how to fix it? Any help would be greatly appreciated.

 

[Altima SSS]

I think it's the automatic transmission control unit (ETC = Electronic Transmission Control) - manual shows the ETC in the same location as your photo. The manual also says it contains the daytime light control module (for Canada models). Does your car have daytime running lights?

 

[Event_Horizon]

Yes, it is the canadian model and does have daytime running lights. The buzzer only stops when I turn the headlights fully on and returns when I shut them off, regardless of what time it is or how light it is outside.

I also checked the transmission fluid level, it is in the high end of the normal range, so it isn't that.

 

[Altima SSS]

Yes, it is the canadian model and does have daytime running lights. The buzzer only stops when I turn the headlights fully on and returns when I shut them off, regardless of what time it is or how light it is outside.

I also checked the transmission fluid level, it is in the high end of the normal range, so it isn't that.

It's obviously something related to the daytime running lights (DTLs). When you turn the headlights on, the DRLs probably go off. If so, the I'd say it's a relay that controls the DTLs that is going bad in the control box, and that's the buzzing you are hearing.

 

[Event_Horizon]

Any idea how to fix it? Replacing the box sounds like the only option. And that sounds expensive. I'm pretty good with electronics, I think I'll try opening the box and seeing whats going on inside.

 

[Event_Horizon]

Woah woah stop everything. Looks like I was wrong.

The buzzing isn't coming from that box. I took that box out and found the buzzing was coming from a second box mounted directly behind the first one. The box itself vibrates violently when the buzzing is taking place. I have removed it and here is a picture of it.
http://img515.imageshack.us/img515/1892/p1020053se8.jpg

It has two six pin connectors on the bottom, and has no markings other then what is shown. I have tried to open it up and look inside but it appears to be a solid plastic box with no obvious way to open it. Any idea what THIS is?

Edit: I have sucessfully managed to open the box and found it houses two electromagnetic switches and some other electronics. I am going to try it in the car to see which of them is malfunctioning.

Edit 2: Ok well it appears that both the switches are cycling back and forth like crazy. It appears that this box is the control unit for the headlights. Without the box, I had no headlight functionality. With the white 6 pin connector only, I had no headlight functionality either. With only the black connector, I had only normal headlights, no high-beams or running lights. But as long as only one of the connectors is plugged in, the buzzing has stopped. For now I have put it back together with only the black connector, meaning I have no high-beams or running lights. But I still have the regular headlights, which are the most important ones. I will spend the next while attempting to trace the running light wires and see if I can find the source of the problem. I have a feeling the problem is not in the box itself. I will also attempt to locate a replacement, if possible.

Unless, of course, anyone has a better suggestion!

 

[Altima SSS]

Sounds like you are making good progress. Hopefully, it's just the black box, but you could be right that a wiring problem might be causing the black box to buzz.

 

[Event_Horizon]

I found the cause of the problem! It looks like the connector on the right headlight was broken and shorting out. I, in my infinite wisdom, didn't bother to check the left headlight to see if it was working or not. I was walking back and forth from the drivers door to the drivers side headlight, and assumed they were both on. I never would have thought the problem was so simple. So I fixed the connector and re-connected the box, and bang, everything works perfect again. Running lights, headlights and high beams. The bulb somehow survived and is still working fine.

So it all comes down to me not being observant enough. I'm really surprised I was driving around with a shorted headlight for a week and never noticed! Thanks for all your help. I'll know where to come next time I have a problem!

 

[OchnofConcrete]

lol

it always seems so simple after you figure it out.

one time my blinkers were acting up.

they would turn on but not blink...

nearly took apart the under dash trying to get a clue.

ended up being the harness was shorting on the cowl because someone in the past had removed the plastic wire protector that wraps around the hole in the cowl in which the harness is threaded through.