Parasitic Draw

[cuddlewuddle]

Hello all!

Recently, my car will be unable to start if left sitting for 3+ days. I just got a brand new battery last week and and new alternator not too long ago so I'm assuming its a parasitic draw somewhere. I hooked up my multi-meter to my battery after letting the car sit for a day and its pulling around 220ma. I pulled every fuse and found the culprit to be fuse #31 or #46. When I pull either one out, it drops to 20ma. With #46 pulled, if I open the door it will jump back up to 220ma, but with #31 pulled, it will constantly stay at 20ma. I am not sure where to start since fuse #31 is shared with many components. Thanks a bunch guys for taking the time to read!

Edit: Definitely Fuse #31. I pulled every other fuse shared with Fuse #31 and Fuse #46 makes it drop temporarily but goes right back up to 220. Also, I made sure both doors were closed as well as the hood and had the trunk open. Waited 20+ minutes and the trunk light would not turn off. How should I proceed if the car doesn't go into sleep mode?

[saneesh8]

Fuse 46 is cruise control right?

Fuse 31 is AC, Clock, Instrument cluster etc etc.

I think it is the cruise control. Can you pull only the fuse 46 and let the car sit for 3 days and see if it works.

Opening door, will make the usage go high for sure. So it should be ok.

Good luck.

[cuddlewuddle]

Fuse 46 is brake light, cruise control, and on board computer(shared with 31). I will try pulling fuse 46 and see what happens. I appreciate the reply!

[rf900rkw]

F31 is keep-alive power to many many different modules. F46 is accessory power, and should have NO effect on a key-off draw test. This is assuming this is an 01 Z3. Not an M, not some other year.

[jclausen]

Once the offending circuit has been found then you unplug each component on the circuit till you find the bad part

[TurboBimmer]

Take a look at the door strike, there is a small plastic switch pushbutton. With time it wears and won't go in enough and will keep some circuit alive.
Compare the driver side with the passenger side, on my car with a slow current draw, that was the problem.

Two solutions, replace the door strike, or add some epoxy glue to build the pin to it's original shape.
The glue will wear eventually though.

[deni2s]

Take a look at the door strike, there is a small plastic switch pushbutton. With time it wears and won't go in enough and will keep some circuit alive.
Compare the driver side with the passenger side, on my car with a slow current draw, that was the problem.

Two solutions, replace the door strike, or add some epoxy glue to build the pin to it's original shape.
The glue will wear eventually though.

This is easy to test if interior light comes off or not in auto mode after 30 secs after the door has been closed (or blinking while driving).

[cuddlewuddle]

I double checked both doors and the plastic switch push buttons seems fine. When I close my doors, the interior light does go off in about 30 seconds. Grrr, I really wish I can find out what's going on. Thank you so much though! Would've never thought of that!

- - - Updated - - -

This is easy to test if interior light comes off or not in auto mode after 30 secs after the door has been closed (or blinking while driving).

Double checked and the light does turn off after 30 seconds. What can it be..... I AM SO CURIOUS

[TurboBimmer]

Pulling the fuses one by one while monitoring the current draw from the battery like you did is the good way of troubleshooting it.
The next step would be to follow each wire (look for the electrical diagrams online) one by one on that circuit to see if there is not a damaged wire etc.

On my previous X5, the owner before me had a localisation anti theft device. I didn't know and a year or so later, the backup battery went dead and was drawing like 2-300 mA and draining the main battery. After isolating the circuit by pulling fuses, I traced the wires and found that cell phone device hidden in a body crease under the rear seat.
Anything is possible.

[nreis02]

I also have a parasitic draw on my z3. For info, I have a 2001 z3 3.0. I went through the same steps the OP did. I also found it to be f31. So looking at the fuse diagram f31 is connected to the clock, instrument cluster, and the anti-theft system. Now, I don't think it's the instrument cluster, I pulled the clock power And there was still a draw. The only thing left is anti-theft system. Is there a away to unplug the system without otherwise harming the car? Or a way to disable it? I don't think my z3 has a anti-theft system, my key only has one button and that turns on a light in the key, it does not lock or unlock the doors.

[cuddlewuddle]

I also have a parasitic draw on my z3. For info, I have a 2001 z3 3.0. I went through the same steps the OP did. I also found it to be f31. So looking at the fuse diagram f31 is connected to the clock, instrument cluster, and the anti-theft system. Now, I don't think it's the instrument cluster, I pulled the clock power And there was still a draw. The only thing left is anti-theft system. Is there a away to unplug the system without otherwise harming the car? Or a way to disable it? I don't think my z3 has a anti-theft system, my key only has one button and that turns on a light in the key, it does not lock or unlock the doors.

Were you able to figure out what was wrong?

[jurgenkoppen]

I have the same issue, fuse 31. Did anyone ever come up with a fix?

[crashgordan]

also following

[stiffnipples420]

hey everyone- I’m also experiencing this issue. F31 keeps blowing on our 2000 z3 2.3 (2.5L). a little background:

car has been sitting in driveway for about a year. when it was running before, it ran great.. at some point, my mom noticed the z3 having performance issues– another diagnosis thread I may have to start later. z3 was parked, and she took the z4 from then on.

fast forward to a week ago– I need to get z3 running in order to pass smog check. it did NOT want to start. didn’t take jump, battery didn’t hold charge. installed new battery (made sure to vent correctly as the old one wasn’t..) and car wants to turn over. I had it barely running while loading it on the flatbed trailer– struggled to stay on, lots of restarts. there is a lot of diagnosing i can’t wait to start!

my problem is here; upon plugging in the code reader to OBDII port on passenger side.. fuse blows. this issue has blown 4 fuses now. i’ve read on other bmw forums to check for bent pins in both female OBD port and male connection from reader, to check trunk wiring harness (although- shouldn’t affect F31/46), and to check headlight dimming switch. so far, those all seem a-ok. next step is disconnecting modules.

side note- after this last fuse blew, i turned key and listened for fuel pump.. operation is normal, but then i heard a low pitched humming sound coming from passenger footwell. similar to maybe.. a blower motor operating at low voltage due to open circuit? couldn’t tell if air was coming out of top vents. humming goes away after key is removed from ignition/switched off. sound stays when key is turned to acc, engine off, no accessories on (radio faceplate removed, all lights and HVAC off).

I have a hunch the culprit causing MY parasitic draw are the HVAC controls. one of the switches is already broken, and I have a replacement unit sitting on the table. fingers crossed, will return to update my findings

[fmcfad01]

Different car, and annecdotal exampe here, but I had an issue 2 years ago with my e39 M5 where the car went into 'Engine Failsafe Mode' and threw a bunch of nonsense codes. During that time, the car was killing batteries, not holding. charge, etc. I pulled the ECU out of the sealed box and found that one of the 5 connectors had a bunch of corrosion on it from what appeared to be fluid creep (coolant) up some of the wiring. Literally as soon as I cleaned this off, everything was fine. As I recall, I had to replace the throttle positions sensors, which was a very annoying job, but after this, everything was good. Not sure if this will help, but it fixed all my car's issues, including the battery drain. Might be worth a check. The thing that lead me to even look was that my ebox fan had been throwing a code for as long as I can remember, and given this all happened when it was super hot/middle of summer, i figured i should replace that in the event this was just caused by overtemping the ECU. The ebox fan is at the bottom of the M5 ebox, requiring you to take everything out. During the course of doing so, i discovered the corrosion on the connector.

[KeysCoupe]

hey everyone- I’m also experiencing this issue. F31 keeps blowing on our 2000 z3 2.3 (2.5L). a little background:

car has been sitting in driveway for about a year. when it was running before, it ran great.. at some point, my mom noticed the z3 having performance issues– another diagnosis thread I may have to start later. z3 was parked, and she took the z4 from then on.

fast forward to a week ago– I need to get z3 running in order to pass smog check. it did NOT want to start. didn’t take jump, battery didn’t hold charge. installed new battery (made sure to vent correctly as the old one wasn’t..) and car wants to turn over. I had it barely running while loading it on the flatbed trailer– struggled to stay on, lots of restarts. there is a lot of diagnosing i can’t wait to start!

my problem is here; upon plugging in the code reader to OBDII port on passenger side.. fuse blows. this issue has blown 4 fuses now. i’ve read on other bmw forums to check for bent pins in both female OBD port and male connection from reader, to check trunk wiring harness (although- shouldn’t affect F31/46), and to check headlight dimming switch. so far, those all seem a-ok. next step is disconnecting modules.

side note- after this last fuse blew, i turned key and listened for fuel pump.. operation is normal, but then i heard a low pitched humming sound coming from passenger footwell. similar to maybe.. a blower motor operating at low voltage due to open circuit? couldn’t tell if air was coming out of top vents. humming goes away after key is removed from ignition/switched off. sound stays when key is turned to acc, engine off, no accessories on (radio faceplate removed, all lights and HVAC off).

I have a hunch the culprit causing MY parasitic draw are the HVAC controls. one of the switches is already broken, and I have a replacement unit sitting on the table. fingers crossed, will return to update my findings

In reply to your side note, the humming sound in the passenger footwell is likely the emissions air pump (SAP) in the engine bay at the base of the firewall. This in not part of the ventilation system, but I could see how you came to that conclusion. This devise pumps fresh air into the exhaust for the first few minutes on start-up to warm up the catalytic converters. This is not likely the cause of your battery drain, unless it continues to run with the ignition off.
-Donny

[MartyBtoo]

Sometimes you don't need to overthink this kind of issue. We have a 2007 Ford Explorer Sport Trac that rarely gets driven. I mostly use it if I need to buy an occasional bale of hay for the horses. It will sit for a month or two and then fire right up. Until it didn't anymore. I would charge the battery for an hour or so, it would start up and charge the battery, would be fine if I started every few weeks. Leave it a month or two, battery dead. Bad alternator, battery connection, mystery short? I finally figured it out by accident; the cell phone charger had been left plugged into the cigarette lighter. Even though the output cord wasn't plugged into anything it would draw enough current to kill the battery. Simple solution, just unplug it when it wasn't being used. No further problem with the battery for several years now.

[Cyclone03]

Our 2001 Z3 3.0 auto does the same thing, if I don’t put a battery tender on it the battery will be low enough to not start the car after 3 days.

It has an after market remote start on it that I suspect because after removing all fuses I have no change in MA draw.