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I have been chasing a battery drain since, well forever. I have searched the forums and read anything from anyone with the same issue, and am coming up short on a solution. I am hoping someone else has an idea for any stones I have left un-turned in my search.
So far, I have removed the audio gateway, tele aid module, Hands free module, CD changer, Head unit, and pulled the #6 fuse.(stereo had been having issues, so I hoped the problem was with one of it's components) I have unhooked the trunk handle (iCarsoft MBII said it might have a short) left both front seat modules unplugged (half the threads on this subject say that HAS to be the problem, but no)
I have had really terrible luck with the local (Seattle) dealership accurately diagnosing other issues using STAR, so they are a last resort to help with this, if at all.
Alternator works fine, keeps the car charged up if I drive every day, or at least every other day, battery is new, and holds it's voltage just fine if left unhooked.
With tens of sensors on modern cars, electric diagrams get pretty complicated, but logically it is still cascade system.
Meaning you have only 1 battery clamp, that can go single or double wire down the car.
The main cable splits on starter and 2 or 3 fuse boxes.
Once you locate those, going down the chart should be easy .
You need to check the current draw when the car is off to see if you're got a current leak. Also in addition to the alternator, you also have a battery control module that can also go bad.
Check alarm siren anti-theft system. The NiCD batteries fail or burn up. Unit is located under the front Left wheel well in the USA. Can be deactivated somewhere in the back fuse/relay panel. Unsure of exactly where and how to. There are threads here about it. Also note that these vehicles have systems that do not go to sleep for up to an hour after the doors are shut so tracing down parasitic current draw can be tricky unless you "trick" the doors/truck/hatch to be closed to allow access and wait for things to shut down.
The alarm battery issue causes the tilt sensor and other related modules to NOT to shut down and then drain the battery overnight. Obviously other malfunctioning systems like the door controllers can do the same nasty.
So, thanks for the ideas. I know I have a draw, because I put an ammeter in line with the neg cable and battery, and after three minutes to allow everything to sleep, I have 1.7 to 2.5 amp draw. Plus the battery goes dead. I have tested the alternator, thinking the diodes might be the problem, but no, they are good. I unplugged the smaller wires in the plug from the battery control module, and still had the drain, so I think I have eliminated that as the culprit.
The Alarm horn/module kept going off when the battery would get low, so I removed it Car alarms are (in my view) completely useless, so deleting it lost me nothing of value.
I am thinking of cleaning it up, charging the battery and trading it in at this point, but am not sure what would be next. I really liked this car, but am not thrilled by a unsolvable electrical problem ruining it. Not sure if buying a w212 version would be good judgment after this.
W212 is whole new technology level, so it can be very nice with whole variety of options, but this is going to cost you.
Even I am qualified in mechanics and had to learn electrics the hard way, I consider electrical troubleshooting way easier than mechanical.
At least you keep your fingers cleaner and no need to craw under the car only to have oil dripping on you.
So if you think the issue goes over your head - spending $200 for indy to troubleshoot is is not a bad deal for the car you like. .... IMHO
How are you monitoring the current draw? Low amp current probe, (clamp). Did you disconnect the alternator. You don't want to pull fuses. You will just keep waking the car up. Watch this video.
Like bankroll said check the fuses without pulling them to locate the bad one(s). In my case i had probably a dozen fuses showing a draw which didn't exactly help, but you may be able to narrow it down to one or two fuses ideally. My total system drain was similar to what you have seen, in my case fluctuating 1.6- 2 amps. Eventually I checked under the glovebox in the passenger foot well and located a board with some corrosion on it. I think it was the BCM which i found on ebay for $30 and solved my problem luckily. Maybe something spilled or got damaged somehow you never know. You could check areas with modules for any issues.
Do you have anything permanently plugged into the OBD II port? In my case the remote power plug for my Valentine One radar detector was drawing current even with the detector turned off (and, of course, the engine off). Valentine reprogrammed the remote plug assembly and the discharge problem went away. With such things as diagnostic aids, aftermarket HUD systems, insurance company driving analysis units, etc. being plugged into the OBD II port, this is definitely something to look into.
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