des-sil-amg

i am having the battery drain on me overnight. ive tried unplugging the seat modules but that didnt work, ive read about the sunroof module but dobt know where it is can someone help me find it?

edtv82

check your headlight switch... i had an issue with mine being set to auto and my battery draining. i had to replace it... good ebay buy.

boohooramblers

Did you unplug the correct connectors to the seat modules?
If so, are you certain that something is drawing current from the battery?

Take the key out of the ignition, turn everything off (i.e. all 'consumers'), close doors, etc. and wait for at least 90 seconds to allow the CAN B databus to go into 'sleeping mode'.

Measure current draw from the battery.
Be sure to use a good multimeter that reads milliAmps.
There shouldn't be a lot of current going to the various functions that DO draw current in 'sleeping mode'.

Here are some of the main ones that will draw current, and this is normal:

Central locking system pump: max. 15mA
Dome lamp: max. 10mA
Electronic radio: max. 20mA
Safety belt extender system: max. 5mA
Anti-theft system: max. 10mA
Electronic time clock: max. 3mA
Electric seat adjustment memory (per seat): max. 1mA

If significantly more current is being drawn, then another 'consumer' is in play.
To test if the Overhead Control Panel (OCP) is drawing a lot of current that would lead to discharging of the battery, check the current across the fuse for the OCP fuse in the rear SAM (fuse: N10/2f9).

des-sil-amg

thanks for the info, i have been checking for current loss in milliamps but its so great that it blew the fuse in my multimeter! but i wasnt waiting 90 secondes before checking ill try that. when i reconnect the battery its a VERY STRONG contact(sparks, crackling). ill try the headlight switch also, if i put it on something other than auto will that help?

boohooramblers

Yep - give the system a few minutes to go into sleep mode and then test current draw.
As edtv82 correctly alluded to, you could have a faulty headlight switch. However, whether switching it to a setting other than 'AUTO' helps the situation, all depends on what the problem is. You could set it to 'OFF', but that's not necessarily going to help. That would be a very easy thing to test though! Certainly test current draw by that circuit if setting it to 'OFF' doesn't work.

des-sil-amg

i listened very carefully and can hear a fan behind the nav, and a slight buzzing sound behind the overhead console like topgunc32(i think thats his screen name) found but he never said what the cure was. if youre out there, how did you fix it?

///AMG4EVER

Pull the CD out of the Nav unit. That should take care of the buzzing noise. if you have a burnt or bad CD in there, it tends to keep spinning and draining your battery.

Another advice, don't plug and unplug things back and forth, you will fry the SAM's eventually.

TopGun32

I still have the same issue

so I just unplug the negative connection from the battery every night if your battery drians over night.

But, if your battery does not last the night.. you will need a new one.

I use my car during the day.. and once I'm home.. I can leave the car over night, no problem.

But a week-end will juice the battery.

I recommend what the guys posted above if you have somebody that can help you. In my case, I'm just dealing with it.

-jc

eclipsed

I did the same for a couple of weeks then my alternator got wiped out from all the charging. try and find the culprit.