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Discussion Starter #1
Right.. Ive been having this problem for a while and havent come to a conclusion yet.. And the reason me posting here is im hoping one of you out there can help me and put my mind back to peace.

Right, so i used to start off with a dead car battery on random occasions when the car has been left for a few hours... It happened first time.. Jump started all was ok.. Hapened again a few days later, jump started all ok again... I then decided to replace the battery to a higher spec.. This lasted fine for a week and a half and died again :(

This happens to me once a week atleast.. So i took it to the auto electrician.. Checked the drain on the battery.. There was no drain.. It was at 0.03A.. This lasted fine for about a week after and something drained the battery within 8 hours while my car was parked while i was working.

Just to let you know, i also have a car voltage checker and its running at 13.8-14v while emgine is running, so battery seems to be charging fine.

So it happened again today and i bought the car home.. Put all the latches on (doors and boot) and waited 30 mins for car to go into sleep mode.. Current was at 0.34A.. So something was drawing the current (also noticed a spark when connecting the multimeter between cable and battery)

I pulled out the first fuse which was for the horn when i did a diagnostic check a while back which dropped the current to normal.. This time i pulled the second fuse and this dropped the current to normal.. Seems like pulling any fuse will kill off the current draw?.. Once killed i cant get the current draw back as its intermittent.

Im at this stage now and i really dont know what to do and its causing me so much hastle.. SOMEONE PLEASE HELP!

Btw i drive a 2005 bmw 318i m sport convertible (e46)
 

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This is a tough one. I had a similar issue with a non-BMW car. In my case, it was CMOS latch up in one of the electronic modules. The module was easy to identify because it would get hot. Wait until the car is back in the high current drain mode and look/feel for warm spots where the modules are. At your drain level (about four watts) that should be enough heat to detect unless it is in a module you can't get to or is spread out.

Your problem may or may not be CMOS latch up. If it is, some event (usually a voltage spike from a motor or solenoid) will cause the latch up condition. The condition will remain until you disconnect power or the battery goes too low. After that, it won't come back until another spike triggers it.

Alternately, you may have some module that is not always going to sleep for some reason or other.
 

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You are correct that 30ma is an acceptable sleeping mode drain, but 340ma clearly puts you up in the parasitic drain category.

I don't think which fuse you pull is the key, I think just the act of pulling any fuse sends a signal to whatever is causing the drain. A change in current may wake up the sleep mode.

I'd want to first try pulling a fuse and seeing what the current measures after you let the car go to sleep. You might have to do this with many fuses until you discover which one was different than the rest.

How and where are you measuring the current drain?
 

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Discussion Starter #4
Hi guys, thanks for your replies.

What modules are you referring to which i can check for any heat?

And the way im measuring the current is disconnecting the negative lead of the battery and then connecting a multimeter in between measuring current.. I noticed there was a spark as soon as i made the connection, i guess this shows alot of current is flowing.

You say pull a fuse and then measure the current and see what makes the biggest difference? Could you clarify this abit more please?

The problem is that the drain is not always there.. It seems to be after a week for example.. I caught the drain yesterday and it was at 340ma.. But, when i disconnecting any fuse, it seemed to drop the current to 10ma.. I plugged the fuse back in, and the drain stayed off and it stayed at 10ma... I was also able to start my car this morning as the drain was killer last night.

What can cause the drain in which pulling any fuse will stop it? Very confused'
 

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Discussion Starter #5
Joegr - also what you mentioned about disconnecting the battery would stop the drain until another spike occurred.. I dont think this is the same case with mine as when i was testing the draw, i disconnected and connected the battery several times.. And the drain remained until i pulled a fuse..
 

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Discussion Starter #6
Gofortheast - what you mentioned about which fuse makes the difference when pulled and letting the car go to sleep, wont this be an issue as the drain is intermittent? I may check all fuses and none make the difference as the drain might not be there?
 

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Joegr - also what you mentioned about disconnecting the battery would stop the drain until another spike occurred.. I dont think this is the same case with mine as when i was testing the draw, i disconnected and connected the battery several times.. And the drain remained until i pulled a fuse..
Yes, your problem is probably different. When you connect the meter you are first disconnecting the battery. After reconnecting through the meter, are you allowing enough time for everything to go back to sleep before being concerned with the readings?
 

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Discussion Starter #8
Yes.. I left the car for about 20 mins before measuring the current draw.. It was well into sleep mode and at 0.34amps :S this seems to be less than the glovebox light which is 0.8A when on :/ confused..
 

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Yes.. I left the car for about 20 mins before measuring the current draw.. It was well into sleep mode and at 0.34amps :S this seems to be less than the glovebox light which is 0.8A when on :/ confused..
But, the meter was connected and turned on for those 20 minutes, correct?

You should see a higher draw when first connected, and then it should drop after 20/30 minutes. Did you see something higher than 0.34A to start with that then dropped some? If so, that would indicate that at least some of the modules are sleeping.

I wonder if there is any BMW tool to plug into the CAN bus with the car off that would tell which, if any, modules aren't sleeping when they should be? I know at least one other car brand that has exactly this for exactly this sort of problem.
 

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Discussion Starter #10
Right.. After my post yesterday, my car started fine in the morning.. However got to work, after work my car didnt start AGAIN! This is really becoming a pain!.. Im waiting for another 20 mins to have a look at the draw again.. I will try pulling a random fuse from a different section of the fuse box.
 

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Discussion Starter #11
Guys just a quick one.. When the car is running at idle the voltage on the battery is 13.8v.. However when i rev the car to 2000-3000rpm it doesnt go above 13.9v.. I read up on a couple of sites that it should be a minimum of 14.2v when revving abd this could indicate a weak alternator or a faulty diode? Can anyone confirm this?
 

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It is my experience that whenever I use the OBC functions to measure voltage, the alternator output is usually 14v or a little above even at idle.
It's just one car's experience, but it would indicate that your car is not charging with a healthy amount of power. And I think it could be a less than perfect battery or the alternator. Of course it could be just the voltage regulator if you wanted to try to economize.
Just for a check, do you turn everything off when you do this test, including the HVAC system completely off?

This would not cure what ails you as you still would have that parasitic drain.
 

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Discussion Starter #13
Ye.. Usually blowers cd player lights everything is off before measuring current.. I havent tried it with everything including the AC yet.. I will do over the weekend.. Reason me asking is it could be a faulty diode in the alternator that is drawing the current.. But would this be cut off by removing a fuse?.. Not too sure..
 

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Discussion Starter #15
Right so this morning my car battery was dead (again).. I jump started it and then took the long drive to work..40 mins..

Once arriving at work, i turned the car off.. I removed the fuse for the blower and heater (to rule out the fsu).. Also my hid's and sideligts were the only thing non standard on the car.. So i unplugged these aswell.. Took a few minutes to do.. Went to check the voltage on the battery and it was 12.54v.. Great..

8 hours later went back to the car and the voltage was 12.4.. So i tried starting the car... Wouldnt turn over again!... Checked the voltage and it dropped to 12.34 after i tried turning it over.. Jump started, drove home (20 mins) and left the boot open but shut the hatch so car went to sleep.. Disconnected negative lead on battery after 20 mins and pit the multimeter in line.. After a few mins it was sitting atound 0.83amps... Way too high!.. It was only me therefore i couldnt pull any fuses and watch current drop.. 3 hours later.. Now at 8pm.. Car is dead! Will not start.. I have officially had enough and will take the train to work tommorow!
 

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Two things
At this point I suspect your battery too. Tell us what happens to the voltage reading when you try to start the car. This could tell us a lot.
And as far as post #13 is concerned, I think you have two problems. Removing the fuse would not have anything to do with a faulty diode.
 

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Discussion Starter #17
When i got to the car.. The voltage was at 12.4v.. When i started it, it didnt start.. So i went to check the reading again and it was down to 12.33-12.34.. Yesterday when i got home however.. After a couple of hours it was at 12.24vabd this started the car.. Could this indicate something sticking aswell? Starter motor?
 

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When i got to the car.. The voltage was at 12.4v.. When i started it, it didnt start.. So i went to check the reading again and it was down to 12.33-12.34.. Yesterday when i got home however.. After a couple of hours it was at 12.24vabd this started the car.. Could this indicate something sticking aswell? Starter motor?
Generally speaking, anything below 12.6 volts (at normal temperatures) indicates either a bad battery or a very discharged battery. Anytime battery voltage goes below about 10 volts, the battery is damaged.

It's not only possible, but likely that your battery has already been damaged too much by all these discharges. It's also likely that your alternator is being stressed beyond what it was designed for by having to recharge the battery so much so often. That said, you really need to find and correct the parasitic drain issue before sacrificing another battery and alternator. I wonder what a dealer would charge to diagnose this problem?
 

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Discussion Starter #19
Well i couldnt seem to find the issue myself and neither has anyone else... Including an auto electrician.. The battery has been jump started so many times i think it must have damaged it quite abit..

Ive called a bmw specialist in cardiff who have bmw dealer equipment and will be taking my car in for a computer diagnostic.. Just to use it will cost me £80.. But they will give me a full report so fingers crossed they will find it..

Problem is it was an intermittent drain.. But i think its become more of a permanent thing now (i hope).. They say they can pick intermittent faults? (God knows how if the faults not there) but ill leave it to them.. Fingers crossed they get it!
 

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The battery has been jump started so many times i think it must have damaged it quite abit..

When i got to the car.. The voltage was at 12.4v.. When i started it, it didnt start.. So i went to check the reading again and it was down to 12.33-12.34.. Yesterday when i got home however.. After a couple of hours it was at 12.24vabd this started the car.. Could this indicate something sticking aswell? Starter motor?
Jump starting your car does very little to damage your battery. Nobody ever said it does.

Starter motor for erratic starting? Yes, classic.
 
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