Something drawing from battery while car is off

Hey all,
 
This is my first time using any forum so bear with me....
 
My girlfriend has a 2002 C240, about 2 weeks ago it wouldn't start, battery was dead.  Boosted it and thought nothing about it until the next day when it didn't start again.  Charged it overnight and took the battery to get tested.  Tested good.  Was carrying the battery back to the car and it exploded.  Went and bought a new battery.  Seemed fine for 2 days and then it was dead again.  Took it to the Mercedes mechanic and they did some tests and found nothing wrong, said it was fine after they charged it.....b/s.  Didn't start again today.  What the heck could be drawing power to kill the battery over night?  Any suggestions?  The drivers side visor light likes to stay on if you don't fiddle with it but we've been making sure that it is off.  Also, the "Lamp Sensor" warning light likes to come on after the battery is charged/boosted.   Any suggestions would be greatly appreciated!  Sorry this is so long.....

Wow,  you have a short.  hard to say where.  But I would disconnect the battery at night to keep the charge.  If you reconnect after that its most likely the alt.  either way good luck.   ( I had a problem like that in my volvo)

Thanks for the info, I'll give it a shot

disconnect the plugs under the seats and see if that helps your problem. the seat control modules draw down the battery. could be the problem.

Thanks, I will have to give that shot too.  I will be trying it this weekend and I will let you all know!  Here is to hoping

Well, I haven't resorted to disconnecting the battery but I have unplugged the fusses for the seat controls and the mirror vanitiy lights, fingers crossed.....

do you happen to have a DMM you could do a quick lil test on the alt that way an if its fine then you have a huge parastic drain cuz a small one an you wont even notice a dead battery unless the car sits over a few days to a week. it cant be a short to power due to that would be blowin fuses left an right, most likely its a switch stuck slightly on on a lose wire to the alt or on the primary wiring to the battery. i would think that the shop would have been able to pick up on something like that. did you take it to the dealer or just a shop?

yeah, no fuses blown, checked that the other night.  took it to a certified mercedes mechanic.  I don't think they tested anything but the battery though.  Might have to go back and talk slowly and preciesly about what's wrong.  Thanks for the help all!