968Forums.com

Our 2003 BMW X5 has a huge (1.4 amp!) parasitic leak to ground, which I've done a lot of troubleshooting on, and since I can't find the offending component, I was wondering if any of the electronics whizzes on this forum might have any ideas as to how I can rig something up to live with it. I've tried multiple BMW forums, to no avail. Here's the summary of the situation, and the steps I've taken to try to pin down the source of the leak:



The battery goes dead if we don't drive it for about two days, so I pulled the fuses, one at a time, and placed the leads of my ammeter across the fuse connectors. It didn't take long to find the offending circuit - the one that controls the stereo/navigation system violently pegs the needle of the ammeter, and there are absolutely no other leaks in any of the other circuits. I'm 100000% certain of this. So, I located a wiring diagram, and one by one, disconnected all the components that this fuse protects, namely the aforementioned stereo/nav unit in the dash, the nav unit's DVD player, the monitors for the DVD player located in the backs of the headrests, and the remote ipod connector my wife had installed a little over a year ago. The leak is still present when these components are removed.



The way I know the size of the leak, and that there are no other sources of leaks, is that I placed a one ohm (to make the math easy), 10 watt resistor in series between the negative terminal of the battery, and the cable that was connected to the terminal. With the offending fuse in place, there's a voltage drop of 1.4 volts across the resistor, which translates directly to 1.4 amps. When I remove the fuse, the voltage drop across the resistor is ZERO, even on the most sensitive scale of the VOM.



So, I probably have a short somewhere in the wiring. I've contacted three mechanics, none of whom are the least bit excited about tearing through the car's wiring harness to locate the leak, and neither am I. So, I'm finally at the main purpose of this post - does anybody have any suggestions as to an elegant way to turn off the parasitic current flow without having to pull the fuse whenever the car is sitting? Is it possible to hook up a relay across the connectors of the fuse, such that when the key is removed from the ignition, the source of current to the relay is turned off? Of course, I still need to have the fuse in the circuit. Here's a picture of the fuse box:



[attachment=9684]



The offending fuse is the one to the right of the red 10 A fuse in the picture. One of the challenges is that it's pretty tight inside the fuse box, which doesn't leave a lot of room to connect standard spade connectors.



Obviously, my first choice would be to find and fix the source of the leak, but the wires from the fuse quickly disappear into the bowels of the wiring harness, which then disappears into the bodywork, so I'm afraid this would really be like looking for a needle in a haystack.



Thanks; looking forward to any suggestions from the collective wisdom of the trusty 968 forums!

Just to clarify, you're not considering powering down the entire stereo/nav unit each time you remove the key from the car, correct? I would think that would require reprogramming on an all-too-frequent basis.

I hadn't thought of that - I just want to rig up something that will accomplish the same thing as pulling the fuse every time the car is turned off. When I pull the fuse, and then put it back in the next time I drive the car, no re-programming is needed - all the station presets are still there, and the navigation system seems to function normally.

i know you said that the leak is still there when the system is removed, but i would still be looking at aftermarket accessories as a drain. many of them have draws (things like phone chargers, and such). aftermarket decks are a big one, and as mentioned, navs are too if they are left on.



if the system was not installed correctly, and they hooked up something to constant hot, that should have been switched hot, then you have found your problem. as an example, a local guy here had that problem with his homelink mirror. the wires up near our mirror are constant hot. this left the mirror constantly on. it would kill his battery overnight. we ran a switched hot wire up there, and the problem was solved.



this could be as simple as your ignition switch not actually turning "off" too. some cars have known problems with their switch.

Flash,



Several good points, but this car is pretty basic - the only aftermarket accessory is the ipod connector, and completely disconnecting it doesn't change the current draw. The ignition switch is a definite possibility, but I think I've come up with decent work-around - I found a connector for an unused relay socket that is hot when the key is on. This connector is in the fuse block that also contains the fuse that protects the circuit with the drain. I'm going to connect this connector to the connector on a relay which energizes the relay, and connect the switch leads of the relay across a wire in the circuit with the drain. This way, when the key is on, the switch in the relay will be closed, allowing the circuit to function, and when the key is off, the switch will be open, cutting off the parasitic current. I admit this is a band-aid, but I'm just not optimistic I'll be able to track down what is probably a very obscure leak. But I definitely welcome all ideas, because ultimately I'd like to fix the source of the problem.