SilverBulletAMG

I just started having this strange electrical issue and have no clue whats up with it. There is something constantly running draining the battery as if you were to leave the lights on yet everything that I can see is off. If I leave the car sitting for more than 24hrs the battery will be dead. All obvious things have been checked. Alternator is great with a constant 14/15 at idle or full load. For grins I even purchased a new battery. When the battery is dead and hooked to a charger it wont charge past 5v, so there is something taking a pretty strong draw somewhere. The other wierd thing is the stereo will turn on with the key removed just by hitting the power button. I have the stock stereo (navigation w/cd changer) but do have a sub and amp hooked up to it. I have had that running for nearly a year with no problem, but when the battery started getting drained the first thing I thought of was the amp and capacitor draining it, so I removed all aftermarket stereo equipment and the problem is still there. I have full aftermarket warranty and will be getting it into the dealership asap but the local stealership is booked out nearly 2 weeks!
I hate electrical issues as its so hard to diagnose but I feel like I'm chasing my tail here. Any and all ideas appreciated!

mbfan03

https://mbworld.org/forums/c32-amg-c55-amg-w203/179139-battery-drained.html

check this post out i had the same prob. havent checked up on it yet but iwll do tomm on my day off.

SilverBulletAMG

Interesting thread, thanks for the link. Funny they mention the seat because my drivers seat was acting strange a few times as well. The forward and back button were reversed somehow, but then would be normal the next time I would check it. Also the bottom portion of the seat will not heat (common problem it seems). It also seems the command is not shutting off as well, which was also mentioned in the other thread. Might have multiple issues going on. I'm going to unplug the seat for now and see if that does anything till I can get it in to be fixed.
Thanks for the link!

SilverBulletAMG

So I just went out and unplugged both front seats and put in a freshly charged battery so hopefully I can make it to work in the morning. After I swapped the battery out and sat in the cab scratching my head with everything powered off and key out of the ignition I heard a fan coming from the stereo. I read in the other thread someone said their nav cd wouldnt stop spooling, so I removed the disc and the fan sound was still there. I'm pretty sure that is at least part of the drain. I have a laundry list of repairs I am taking with me to the dealer and will fill everyone in with the outcome once it's completed.
Thanks again!

mbfan03

sure do fill me in, i havent check up on unpluging anything yet becuase i havent had the time but my seats were acting normal and heated part was waring so i dont know if that is the issue with mine and as the command part i have a pioneer double din nav system.

ultraman206

The bottom heated seats not heating is a seperate issue from battery draining.

The most common cause for the battery drain issue are failed seat control modules (internal short parasitic draw). Note: my seats were functioning normally when I had the problem. If after disconnecting it and you still have the problem; I would check your sub/amp connections again... sounds fishy that you can power your stereo on with keys removed. The fan noise may just be your ventilation system etc.

Also, you may run into problems with your aftermarket warranty.. make sure your dealership accepts your warranty and covers these issues. Good luck.

SilverBulletAMG

Yes, I know. It's just one of MANY issues I am going to address when I bring it in. The fan noise isn't the ventilation system. I pulled the stereo and it is the fan constantly running making the noise and most likely causing the drain or that plus the seat control module. Either way I have everything on the seat disconnected along with the stereo now. All connections for the sub/amp/cap were fine but I have an inline 100A breaker that I just turned off to cut power to that as well.
As for the warranty, it is "supposedly" bumper to bumper on everything minus obvious items like wiper blades and whatnot. They better cover all this crap!

ultraman206

Hope you get it all squared away... do let us know what the dealer says.

Boyo*C32AMG*02

I had the same problem happening to my car a week ago.Bought a brand new battery,start the car up and it was running fine.Left the car in the garage over night,hit on the unlock button in the morning and the battery just when dead again.Tried to jump start, but the car was just not responding,i couldnt even get the car to crank up,not even once.Called the 24hr service guy,he came by with a fully charge battery, connects the jumper cables and he got the car fired up.He drove it back to the dealers and rectify that the problem was coming from the electric seat relay unit, its a square black box with connector ports on both sides (looks like those usb ports you see on your computer)except those ports are a little bigger,situated under the seats.He told me that this is a common problem on the (W203)models,especially when the usage of the electrical seats are often being used,it will than burn out one of the components inside the relay box and this causes your battery to be drain of fairly quick,especially when your car is at a standstill.
I had it replaced and reset my ECU aswell.The car just fly's of now, as if the first time i got it from the dealers.Hope this explaination help's!Gd luck!

mbfan03

i guess it that time for these things to be goin bad. i dont have warranty and tonight i discovered my bottom portion of the seat isnt heating, and my battery is draining. do you know if that control controls both the heated seat and the cause of the drain on the other hand. for us with no warranty does anyone have any idea how much that piece cost?

SilverBulletAMG

Still waiting for the dealer to call me and "squeeze me in". I will post the totals when I get mine repaired.