Hi everyone, I'm a relatively new poster but have lurked the form for months now. In August 2005 I bought a black E39 97 540I 6 speed. The car does not have any mods other than a M5 carbon fiber rear spoiler, M5 copy wheels, cross drilled rotors and a Dension Ice Link for my Ipod that I installed myself.

I didn't notice it when I first bought the car but after owning the car for several months I have noticed a humming or faint buzzing noise coming from the area of the dash just below the factory radio. It sounds very much like an electric motor and you can hear it even with the car off and the keys out of the ignition. I thought this was strange but it never drained the battery down. Then today I got in the car and it was dead. All the dash lights come on, as well as the interior lights but when I try to turn it over, I just get a clicking noise. Now I have no idea what caused the battery to drain down and while it could be that humming noise coming from the dash, I doubt it since that noise has been going on since August of 2005.

So my question is, does anyone have an inkling as to what that electric motor noise might be coming from just below the factory stereo? The dead battery is another matter altogether...

sux 4 u

That humming noise you hear just after shuttting off the car is probably the sampling fan for the Climate Control Unit. They can get get dirty an make a bit more noise than usual.

Parts of the car stay alive for about 15 minutes after you shut off the car and close the doors. After that the car "goes to sleep" and the battery draw drops to about 30-40ma, which won't drain the battery for days. You can tell if that happens because all of the lights & such go out. Opening a door or unlocking the car wakes it up, so just look in a window to see if it does go to sleep.

It could well be that your battery has just reached the end of its useful life. If the battery is over four years old I'd say to just replace it. If the problem reoccurs a check for parasitic draw would be indicated.

That humming noise you hear just after shuttting off the car is probably the sampling fan for the Climate Control Unit. They can get get dirty an make a bit more noise than usual.

Parts of the car stay alive for about 15 minutes after you shut off the car and close the doors. After that the car "goes to sleep" and the battery draw drops to about 30-40ma, which won't drain the battery for days. You can tell if that happens because all of the lights & such go out. Opening a door or unlocking the car wakes it up, so just look in a window to see if it does go to sleep.

It could well be that your battery has just reached the end of its useful life. If the battery is over four years old I'd say to just replace it. If the problem reoccurs a check for parasitic draw would be indicated. Thanks for the info. Now that you mention it, the noise does seem to come from somewhere close to the Climate Control Unit.
But if I leave my car parked in the garage overnight and get in it the next morning without putting the keys in the ignition, you can still hear that noise. Is there anything on the net that can tell me step by step how to clean the Climate Control Unit fan?

check to see if the aux fan is still running

check to see if the aux fan is still running
When you say aux fan, are you referring to a fan inside or behind the Climate Control Unit, or located somewhere else? Having only owned this car for a few months i'm still learning :)

That humming noise you hear just after shuttting off the car is probably the sampling fan for the Climate Control Unit. They can get get dirty an make a bit more noise than usual.

Parts of the car stay alive for about 15 minutes after you shut off the car and close the doors. After that the car "goes to sleep" and the battery draw drops to about 30-40ma, which won't drain the battery for days. You can tell if that happens because all of the lights & such go out. Opening a door or unlocking the car wakes it up, so just look in a window to see if it does go to sleep.

It could well be that your battery has just reached the end of its useful life. If the battery is over four years old I'd say to just replace it. If the problem reoccurs a check for parasitic draw would be indicated.

+1

Mine has the same noise in the dash. It is intermitent now (after shooting canned air and electronics cleaner in the slots in the lower left corner of the console). And I'm sure it's like the light in the fridge that shuts off when you shut the door and comes back on when you open it.

And BMWs act VERY STRANGELY with low battery power (which can result from not being started on a regular basis for weeks/months/etc.). Mine seemed possesed with a low battery because the radio would shut down at random intervals.

Good luck with the car. I really enjoy mine, but sometimes wish I'd found a 6-speed.

Sound like you're due for a new battery anyways.

Or you may want to see if you can salvage your old battery.

Peel off the BMW labels on the top of the battery and it should reveal the fluid caps. Fill up the battery with distilled water and then put it on a charger. You got nothing to lose! :cool

If all fails, just get a replacement battery from Federal or wherever you can get one that meets the same spec as the factory battery.

But if I leave my car parked in the garage overnight and get in it the next morning without putting the keys in the ignition, you can still hear that noise.
As soon as you open a unlock or open a door the car wakes up, which should turn on the sampling fan. Next time leave a window rolled down and check for the sampling fan being off by leaning into the car (leave the alarm off) 20 minutes or more after parking the car.

if you have the AUTO HVAC system...the buzzing noises you hear are the stepper motors etc. resetting themselves to their default position. It's not just the "sensor fan" that's making noises as it draws the cabin air across itself to maintain the selected temperature.

If you want to clean it (the sensor fan)...there are tons of info on removing the HVAC control unit on the internet...go to a site like www.bmwtips.com ... or try using some "keywords" in the search link on this site.

As others have stated...if you have the original battery from 1997... your battery has done very well and given you great service...its time to replace it now. :D

thejlevie beat me to it...I was going to suggest rolling down your window when you pull into the garage...and after 15-20 minutes...go back and check to see if you hear the buzzing...because as soon as you lift the door handle...the car will..."awake"...bimmers have a soul...I thought you knew that. ;)

Lots of great info, thanks alot guys! :)

As I said, i'm still learning about the car so I apologize in advance if I ask any redundant or "stupid" questions.

Okay, I have made a lot of post on this subject of DEAD BATTERIES IN E39 540'S. If I leave my car parked for 3-4 days, the battery is dead and all I hear when I try to start it is a clicking noise......... I have replaced the battery,,,,,,NO LUCK. I have replaced the final stage resistor to the cabin fans,,,,,,,,,,,,,,,NO LUCK........ ROADSHOW BMW OF MEMPHIS COULD NOT FIND THE DRAW......... They check the alternator, starter, and battery,,,,,,,NO LUCK. I need someone who is "SMART" because the dealership is "STUPID". I am living testament that the dealship does not know everything, all they have is a pretty building and a lot of overhead.

You can find it by hooking up a current meter in series with the battery and then pulling the fuses one by one until you find the draw. Do a search for this procedure and I'm sure you'll find it.

There are a few problems here that sound like a problem I am experiencing.

ForceFed7: Are you sure it is a Aux Fan and NOT coming through the speaker system? I thought mine sounded like something coming from behind the dash, turns out it was static coming from the front right speaker. If would be certain by putting your ear up to each speaker when the problem exists.

Jet540i6: I have the same problem. Battery is new, starter, alternator, ignition switch, and charging system all check out ok. I have static coming from the front right speaker. I believe the cause is a failing DSP amplifier unit putting an extra drain on the battery. The problem can be fixed by unplugging the DSP unit or removing the fuses. Unfortunately, my radio wont' work then either.

Does anyone have a wiring schematic for the 540 they can post a link to? If not, one for just the DSP stero system? I'm too lazy to purchase a $90 bentley manual.

Hope this is helpful to some, I'll keep you up to date on my findings.

There are a few problems here that sound like a problem I am experiencing.

ForceFed7: Are you sure it is a Aux Fan and NOT coming through the speaker system? I thought mine sounded like something coming from behind the dash, turns out it was static coming from the front right speaker. If would be certain by putting your ear up to each speaker when the problem exists.


Does anyone have a wiring schematic for the 540 they can post a link to? If not, one for just the DSP stero system?
Hi Atl93FD, I know for a fact it is not static coming from the speaker as I have audibly traced the noise to behind the Climate controls. It took me all of about 10 seconds to figure out where the noise was coming from. The DSP comment has me wondering though as I have removed my 6-disc changer and installed the Dension IceLink unit for my Ipod in there. I'm wondering if the Dension unit is putting an extra draw on the battery. I remove the Ipod and pull it out of its charging cradle whenever I exit the vehicle but maybe its the Dension firmware unit draining the battery?

You can find it by hooking up a current meter in series with the battery and then pulling the fuses one by one until you find the draw. Do a search for this procedure and I'm sure you'll find it.

Excellent idea, thanks! :D

I forgot to mention that earlier tonight I had driven the 540 over to a friend's house to have dinner and when I left his house afterwards, I realized that none of the gauges on the instrument cluster were working. No tachometer, speedo, fuel or temperature. I stopped at the next stop sign, shut the car off and then restarted and the gauges worked fine.

Then I went down the road a little ways and tried to turn on the stereo to listen to my Ipod and the stereo wouldn't turn on. So I pulled into a gas station, shut the car off again, restarted and then the stereo worked fine.

I'm wondering if this may or may not have something to do with my newfound battery problems. I also noticed that when I would come to a stop light and push in the clutch, the idle would drop down to about 250-300RPMs, the headlights would dim, the interior lights and the dash lights would also dim. At first glance it seems like the battery is not charging while the car is running but my gut feeling tells me there is more to this. :(

Hi Atl93FD, I know for a fact it is not static coming from the speaker as I have audibly traced the noise to behind the Climate controls. It took me all of about 10 seconds to figure out where the noise was coming from. The DSP comment has me wondering though as I have removed my 6-disc changer and installed the Dension IceLink unit for my Ipod in there. I'm wondering if the Dension unit is putting an extra draw on the battery. I remove the Ipod and pull it out of its charging cradle whenever I exit the vehicle but maybe its the Dension firmware unit draining the battery?

I also have the dension icelink for my ipod. Dension swears it isn't the problem, but who knows. I had the Dension kit for 6 months without a problem, then problems started (it could be conincidence).

If anyone can help me find a wiring schematic I'll find the drain using a multimeter and post results.

Well here is my observations with the Dension kit, FWIW.
I have noticed that if I leave the Ipod in the Dension cradle and turn the car off with the stereo on and come back later and get in the car and turn it on that the Ipod will be on a totally different song than when I turned the car off. In fact, it will usually be anywhere from 3-6 songs later, which means the Ipod is still running for a good while even after I have exited the vehicle. This could mean that the Dension firmware hardware unit(the part that houses the chip) could be drawing power from the battery even after the car has been shut off or even after the car has gone into "sleep" mode, of course I haven't proven it yet.

On the other hand, if I shut off the stereo before I exit the vehicle and manually shut off the Ipod but removing it from the cradle and shutting it down then obviously I pick up where I left off earlier, songwise. But this still doesn't tell me whether the Dension Firmware unit is still drawing power with the car off. As per Dension you tap into the DSP amplifier's power source to power the Dension unit.

Well here is my observations with the Dension kit, FWIW.
I have noticed that if I leave the Ipod in the Dension cradle and turn the car off with the stereo on and come back later and get in the car and turn it on that the Ipod will be on a totally different song than when I turned the car off. In fact, it will usually be anywhere from 3-6 songs later, which means the Ipod is still running for a good while even after I have exited the vehicle. This could mean that the Dension firmware hardware unit(the part that houses the chip) could be drawing power from the battery even after the car has been shut off or even after the car has gone into "sleep" mode, of course I haven't proven it yet.

On the other hand, if I shut off the stereo before I exit the vehicle and manually shut off the Ipod but removing it from the cradle and shutting it down then obviously I pick up where I left off earlier, songwise. But this still doesn't tell me whether the Dension Firmware unit is still drawing power with the car off. As per Dension you tap into the DSP amplifier's power source to power the Dension unit.

Dension is hardwired off the battery, always draws power.

Dension is hardwired off the battery, always draws power.
Well the directions I got told me to wire my Dension unit to the power wire for my DSP amp so my Dension gets its power from the amp and is not directly wired to the battery. I do not know if the wire I tapped into on the amp is constant power.