Help please guys! Electrical nightmare:(

Hi,

Could really use with some advice from people much more mechanically minded than me! I've got a 3 series 318i year 2000. Basically I have to unplug the battery every time I get out of the car or it will not start when I go back to use it. Obviously a battery drain. I have had it in 2 garages, one changed the climate control unit and the other said I need a new engine management system which I didn't agree with. The problem persisted and I have taken it to a auto electric centre who tested it and said it was fine!!, they cleaned the ignition barrel saying it could not be turning everything off properly. I got it back and after 2 days I went to use it and its flat again. Any help would be appreciated........ It's had a new battery, new alternator, which I have tested again, new terminal leads on the battery, it has no engine management lights on the dash? Thanks again

Perhaps one idea is to look through the fuse reference card and pull fuses for everything you can live without until the battery stops going flat. Then add them back in a bit at a time (more important ones first) over the course of a few weeks.

If you have a multimeter, you can hook it up as you remove / reinstall fuses to see if there's a voltage rise or drop when removing or reinstalling a fuse, one at a time. If you notice a larger drop in voltage for a particular fuse, that may be a clue to see what that fuse powers and start investigating from there.

Good luck!

If you are going to search your self, you need an ammeter rather than a voltage meter. You disconnect the batter and hook up the ammeter between the batter and the cable. The trick is, you need an ignition cycle to "wake up" all the electonics and get them working property so you can then do your search. I have an adapter that goes between, with a knob on it. You connect it, close the connection with the knob and start the car and let go through a run cycle. Just a few seconds will do the trick. The adapter has two "pins" on it to connect your ammeter to on either side of the knob, and wtih the ammeter connected and turned on, you open the adapter connection with the knob. Now, the electronics are all "awake" and working, and all the amperage flowing into the car is going though the ammeter so it can give you a reading. You want the amperage to be under 50 miliamps usually. If's it high, start pulling fuses one at a time to determine what circuit the issue is in. When you see it drop down below that 50 miliamps, you just found the circuit. From there, you have to begin searching just within that circuit to find the component that is causing the draw.

You can also use an induction ammeter but they are for measuring much higher values and may not be precise enough to pick up smaller draws. Keep in mind that a circuit can draw 12 volts, but nearly no miliamps. So voltages are really not the thing to look for. You do want to be careful not to try and start the car with an ammeter "in-line" as it will blow the fuse(s) in the ammeter. My Fluke87 has a max 15 amp fuse (if I remember correctly) so trying to start it would pop that fuse in a heartbeat.

Make sense?

Absolutely. Thanks for the advice. Will give it a go soon as possible. Thank you both for taking the time to reply. Greatly appreciated.

Originally Posted by VP

If you are going to search your self, you need an ammeter rather than a voltage meter. You disconnect the batter and hook up the ammeter between the batter and the cable. The trick is, you need an ignition cycle to "wake up" all the electonics and get them working property so you can then do your search. I have an adapter that goes between, with a knob on it. You connect it, close the connection with the knob and start the car and let go through a run cycle. Just a few seconds will do the trick. The adapter has two "pins" on it to connect your ammeter to on either side of the knob, and wtih the ammeter connected and turned on, you open the adapter connection with the knob. Now, the electronics are all "awake" and working, and all the amperage flowing into the car is going though the ammeter so it can give you a reading. You want the amperage to be under 50 miliamps usually. If's it high, start pulling fuses one at a time to determine what circuit the issue is in. When you see it drop down below that 50 miliamps, you just found the circuit. From there, you have to begin searching just within that circuit to find the component that is causing the draw.

You can also use an induction ammeter but they are for measuring much higher values and may not be precise enough to pick up smaller draws. Keep in mind that a circuit can draw 12 volts, but nearly no miliamps. So voltages are really not the thing to look for. You do want to be careful not to try and start the car with an ammeter "in-line" as it will blow the fuse(s) in the ammeter. My Fluke87 has a max 15 amp fuse (if I remember correctly) so trying to start it would pop that fuse in a heartbeat.

Make sense?

dont know if i'd agree with you on the bolded comment... when testing for parasitic draw you're trying to get your car to be in the same condition it would be in when you leave it in the garage over night (key out, doors locked etc..) that way you can minimize the number of active circuits and determine which one is drawing unnecessary amperage.

i'd recomend using ur DMM to read voltage drop over each fuse to determine which circuit is live. would be much faster than pulling fuses one by one.

Locate your fuse box and get access to it. It think it's in the glove box in your car.
Disconnect the negative battery terminal. Connect your ammeter in series - so one lead will go to the disconnected negative terminal that normally goes on the battery and the other end goes to the bare battery post.
Open all your doors and trunk lid, but use a screwdriver and trip all the latches to the position they would be if they were shut. Lock the doors, just as you normally would if you were leaving the car. The ammeter will probably show about 300 mA at this point. This number will drop in phases as different components go to sleep.
After about 20 minutes, all modules should be asleep and current draw should be about 30 mA, but anything below 50mA is probably OK.
If the current draw is too high, start pulling fuses (do not replace until this is done), check the ammeter after each one until it drops. If any single fuse reduces the current draw by more than 20 mA, make a note of that circuit. Keep going until you're below 50 mA.
Now you can wake the car up by unlocking and "opening" the doors.
Replace the fuses.
Investigate the circuits with high current draw. Figure out what is on each of those circuits.
Repeat the above process, but instead of pulling fuses, disconnect the individual components on the circuit until you find your current consumer.

Have you installed any aftermarket accessories, especially stereo equipment?

Originally Posted by vavet5308

Locate your fuse box and get access to it. It think it's in the glove box in your car.
Disconnect the negative battery terminal. Connect your ammeter in series - so one lead will go to the disconnected negative terminal that normally goes on the battery and the other end goes to the bare battery post.
Open all your doors and trunk lid, but use a screwdriver and trip all the latches to the position they would be if they were shut. Lock the doors, just as you normally would if you were leaving the car. The ammeter will probably show about 300 mA at this point. This number will drop in phases as different components go to sleep.
After about 20 minutes, all modules should be asleep and current draw should be about 30 mA, but anything below 50mA is probably OK.
If the current draw is too high, start pulling fuses (do not replace until this is done), check the ammeter after each one until it drops. If any single fuse reduces the current draw by more than 20 mA, make a note of that circuit. Keep going until you're below 50 mA.
Now you can wake the car up by unlocking and "opening" the doors.
Replace the fuses.
Investigate the circuits with high current draw. Figure out what is on each of those circuits.
Repeat the above process, but instead of pulling fuses, disconnect the individual components on the circuit until you find your current consumer.

also thought i'd point out that you want to make sure the ground strap is never completely disconnected... you want to put ur ammeter in series without losing power to everything in your car. this can and will cause suspect control units/components to reset and possibly stop drawing current like it was doing before... this will give you headaches especially when you are trying to track down intermittent consumers..

Originally Posted by alpinweiss

Have you installed any aftermarket accessories, especially stereo equipment?

No I have not installed any different stereo equipment. Thank you

Originally Posted by chansta

dont know if i'd agree with you on the bolded comment... when testing for parasitic draw you're trying to get your car to be in the same condition it would be in when you leave it in the garage over night (key out, doors locked etc..) that way you can minimize the number of active circuits and determine which one is drawing unnecessary amperage.

i'd recomend using ur DMM to read voltage drop over each fuse to determine which circuit is live. would be much faster than pulling fuses one by one.

I spoke with a mechanic this past weekend because I'm having a slow crank situation with my car. The car needs to be asleep to take the measurements, otherwise the method is as described to me.

He suggested leaving the trunk open, and the right side front window open, glove box and fuse panel exposed. Set your DVM to read ohms and let the car go to sleep. Next, pull fuses until the draw goes down and you've found your parasitic drain.

He said the FSR (final stage resistor) that controls the climate system is a common cause. You might want to start there. Set everything up, leave the right side front door open, let the car go to sleep, check the measurement, reach up and unplug it, read again.

Originally Posted by jvr826

I spoke with a mechanic this past weekend because I'm having a slow crank situation with my car. The car needs to be asleep to take the measurements, otherwise the method is as described to me.

He suggested leaving the trunk open, and the right side front window open, glove box and fuse panel exposed. Set your DVM to read ohms and let the car go to sleep. Next, pull fuses until the draw goes down and you've found your parasitic drain.

He said the FSR (final stage resistor) that controls the climate system is a common cause. You might want to start there. Set everything up, leave the right side front door open, let the car go to sleep, check the measurement, reach up and unplug it, read again.

Ok sorry I wasnt clear. By doors locked I meant to have them open but trip the door switch so that the car thinks its closed. Same with trunk this way you have access to the fuse boxes to test for voltage drop.

I say voltag drop instead of pulling fuses because in a live circuit even a fuse will cause a small amount of voltage drop. So instead of pulling fuses on circuits that's possibly not even live, u
U can determine which fuses are on a live curcuit so u don't waste as much time

Originally Posted by jvr826

I spoke with a mechanic this past weekend because I'm having a slow crank situation with my car. The car needs to be asleep to take the measurements, otherwise the method is as described to me.

He suggested leaving the trunk open, and the right side front window open, glove box and fuse panel exposed. Set your DVM to read ohms and let the car go to sleep. Next, pull fuses until the draw goes down and you've found your parasitic drain.

He said the FSR (final stage resistor) that controls the climate system is a common cause. You might want to start there. Set everything up, leave the right side front door open, let the car go to sleep, check the measurement, reach up and unplug it, read again.

All completely solid advice, except that the really proper way to do this is to open the battery circuit and insert an ammeter in series with the car. This to measure parasitic current drain.
If I recall correctly, should be under 50ma when car is asleep. The only meaningful mode to measure in.

Last sumer, I noticed my blower continued to run after turning the engine off and it killed my nine month old battery. I pulled fuse 50 when the car was parked until I figured out the problem. It turned out to be the aftermarket FSR that I installed a few months before.

Originally Posted by chansta

dont know if i'd agree with you on the bolded comment... when testing for parasitic draw you're trying to get your car to be in the same condition it would be in when you leave it in the garage over night .

Thanks for catching that. Yes, indeed, what I typed and what I meant do not match. When I typed "wake-up" I meant the be powered up and cycled (meaning back to sleep) rather than simply have the power cut. In my experience, solid state components will keep drawing power if they have not been powered up and cycled - cycled meaning what is usually called "sleep mode" after an ignition cycle. This draw will give you incorrect readings on your meter. So it is critical step in getting true readings ... and I should have explained it better.

Originally Posted by VP

Thanks for catching that. Yes, indeed, what I typed and what I meant do not match. When I typed "wake-up" I meant the be powered up and cycled (meaning back to sleep) rather than simply have the power cut. In my experience, solid state components will keep drawing power if they have not been powered up and cycled - cycled meaning what is usually called "sleep mode" after an ignition cycle. This draw will give you incorrect readings on your meter. So it is critical step in getting true readings ... and I should have explained it better.

np i do that often.

Hi all I am newly registered but have been lurking for a while.

VP, could we get a link to the adapter you mentioned? It sounds like exactly what I am looking for. I promise i tried searching it. I would like to simulate the real world driving conditions as much as possible. This is a good thread, thanks everyone.