I've been lurking since I bought my non running Pepper 06MCS last year. I got a great deal on it and got it running pretty quickly. I now have at least 40 hours working on it and it really works great, I love this little car. Using advice found here and Youtube, I've changed the clutch, oil cooler driveshaft boot, tie rod ends and have serviced the supercharger. The last major problem is this pesky voltage drain. I made a few workarounds to minimize it so things that should be powered all of the time are only powered when the key is on, i.e. Fuse 23. Still there is a draw on the battery when off. Has anyone ever really solved a voltage leak here? And if so, how?

 

Not on our Mini, but I had a similar issue on a 2001 VW Jetta. I had a current draw that would drain the battery after a day or so of sitting. Every check I made showed all systems using only their required sleep current when the vehicle was off and sitting.

In the end, what I discovered is that there was a leak path back through the alternator. I couldn't meaure this checking on the draw of the vehicle side of the battery, it was only when I accidentally checked on the alternator feed path that I found it. It was likely the result of a leaky diode in the alternator's output regulator. I replaced the alternator and the current drain problem was solved.

And just for further detail, the alternator's output was fine. It would charge the battery fine when the engine was running, it was just that there was a leak path when sitting.

 

Current draws can be very aggravating.

If you know the draw is on the circuit that fuse 23 serves, that is a huge advantage. You will need to measure current draw with a multimeter than can measure to 0.025 amps. If you have an amp clamp that can measure that low, put it on the battery negative cable. It your multimeter only has test leads, you'll need to put the meter in AMP mode, with the test leads in the proper ports (usually not the same port as for measuring voltage) and put your meter in series between the negative post on the battery and the negative cable. With the switch in AMP measuring mode, you will be able to see the current draw. Generally, the maximum current draw specification is 0.025 amps. A draw that drains the battery overnight will probably be around 1 amp or so, maybe more.

The problem with putting your meter in series is that when you connect the circuit with your meter, the car will "wake up" and many modules will be drawing current in this state, so you must wait a couple of minutes or so for the modules to go back to sleep before you can assess the current draw. All door latches should be set in closed mode (doors open so you can get inside the car without waking it back up), including the boot and hood latches. When the car is asleep, if you observe the current drawing too much, go to that circuit (the components on fuse 23 in your case) and begin unplugging components on that circuit until you unplug one that causes the draw to drop below 0.025 amps.

Pro tip: if something on that circuit has a section that moves often (a sunvisor with a lit vanity mirror for example), suspect that component. I have seen wires in the pivot point wear through their insulation and touch each other enough to create small current draw.

 

I bought a clamp meter and tried to isolate the draw but so far I found where it isn't drawing from. The alternator is not the cause of the leak, which I was hoping for as it is the easiest to replace. The BCM is next.

 

Another thought - is there any aftermarket electronic equipment installed? Dashcam, radio, etc.? If there is, then verifying the quality of any wiring in their installation would also be a point to check.

 

I have not installed anything on the "on" side of the ignition switch, only adding a USB port to the cigarette lighter.

 

Last battery drain I had turned out to be the tach module. Intermittent / dead tach function, weird idiot light combinations even after the key was removed. Battery would be drained in under five days if I didn't drive it. Probably not your issue but easy enough to swap in a new-to-you unit if you run out of other ideas.

 

I found a gps tracker wired into the obd2 port of my car. That fixed the parasitic drain I had.

 

just curious did you figure out how it got there, and did you go personally thank the individual(s) responsible?

 

here's a post i wrote about it
https://www.northamericanmotoring.co...ml#post4613395

essentially, i just kinda stumbled upon it. and this car has been passed around so there's no telling who is responsible for it.

 

I've got 2 2004 R50's. One is my daily driver, the other is a project we bought for $400 that is now my 16 year old's first car.

This second one had a draw that drove me nuts for a little while. No codes, and it started with no issue if driven the next day. But, if it sat for 2+ days we had a weak battery and no start without jump. My son had noticed a ding like the lights were on or key was in the car at times when just getting in or opening the door (I forget exactly). We disconnected door latch switches, ignition switch, and anything else we could think of.

Our issue ended up being a bad hood latch switch...after replacing that...no more issues.

Good luck and happy hunting!

 

I unplugged each of the door and latch switches and found no change. I am wondering if the BCM could be responsible.

 

I'm not inclined to blame an ECU without signs of visible damage or corrosion from water ingress. Having worked at Tier1 electronics suppliers most of my career, the level of testing and quality that has to go into the design and construction of these modules make them a last-likely source of failure (except if some sort of design issue emerges after time in service).

If your issue (current drain) isn't matching a whole bunch of other BTDT evidence that points to the BCM, I don't know that replacing it will solve your issue. If you have a spare one lying around to try or can pick a known working one up for cheap, then it would be worth a try as you continue to troubleshoot the issue. Just my $0.02

 

Sorry it had been a while since we had this issue but I just remembered our hood latch issue was related to the factory alarm system the previous owner had unplugged. Once we plugged in all the alarm components we were good…the last was the hood switch. If you have a factory alarm, here’s a link to a wire diagram for those circuits:
https://tinyurl.com/Alarmdiagram

 

Thanks Chris. I'm still working on this problem and will write something here when I finally find the problem.