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2001 C320 seat control module

Discussion in 'Automotive Electronics' started by cesguerra, Mar 7, 2012.

  1. cesguerra

    cesguerra New Member

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    I have a 2001 C320 seat control module that drains my battery flat overnight. There are three wires in the harness. A ground wire and two power wires, one that is energized by turning the ignition on and one that has constant power. The latter is for the convenience mode which pushes back the seat and puts the steering wheel out of the way for easy in and out access to the drivers seat. This constant power wire is what drains my battery and the mercedes forum suggests splicing this wire to the ignition only wire so no power is drained when the keys are off the ignition. What I am afraid of is overloading the ignition only wire. if I do this, is it possible to put a relay? Is there an advantage in putting a relay? If there is, can I use the existing three wires to hook up the relay and are there any better suggestions in wiring the relay. I don't have a problem losing the convenience mode. I can live with that. I just want to avoid draining my battery and also avoid spending for 2 new control modules which costs around $500 each from the stealership and a possiblity of these new modules to do the same eventually. Need Help in getting this car ready for my new teenage driver.

    Thanks Folks
     
  2. Diver300

    Diver300 Well-Known Member

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    Firstly, I would measure the current that the module is taking. To drain a car battery overnight, something would have to be getting warm. You would need to take around 2 amps overnight to drain a car battery that is in reasonable condition.

    The advantage of putting in a relay is that you won't overload the ignition wire. The relay will only take about 200 mA when the ignition is on, and nothing when the ignition is on.

    You need to wire a relay as follows:-

    Leave the ignition and ground connections connected to the control module.

    Connect ignition and ground to connections 85 and 86 of the relay as well.

    (At this point check that the relay clicks when you turn on the ignition and clicks again when you turn off)

    Cut the constant power connection to the module, and connect the two cut ends to connections 87 and 30 on the relay.

    You could put a time delay into the relay so that it turns off a minute or two after you turn off the ignition, which would restore the convenience mode, but that is more complicated. I added a delay like that to one car so that the windows could be shut after the ignition was turned off.

    If the seat control has memories, those could be lost if you turn off the power. I guess you aren't worried about that.
     
  3. CINELLImotorsports

    CINELLImotorsports New Member

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    Why not just adjust the seat to a comfortable position.. and unplug the module?

    If you want to test which module it is..just put the seats all the way back (on the bottom adjustment) and all the way up (on the bottom adjustment); roll down all the windows; pop the hood, but then close the latches so the vehicle thinks that the car is locked; then access the batter under the Fresh Air Filter housing and loosen but dont dissconnect the negative terminal. next get a DVOM and begin to get ready to hook the meeter up in line on mA reading. Lock all the doors (if there's something open the vehicle will not lock so if you do all the steps right and have all the doors and latches closed then you'll see the lights blink and the locks lock... now.. without losing the connection get the amp meeter in line... it's not that hard to do just before the terminal comes off the post of the batter slide your second gator clip under it and get it on the post.. if you mess up you'll know.. the alarm with go crazy and with your head under the hood you'll probably get a nice spook.

    if all goes well, let the car sit for 5 - 10min then you'll see it still high when the w203 goes to sleep there's practically no draw. after a little bit, reach into the window DONT OPEN THE DOOR and reach under the seat and dissconnect the module.. then go look at the meeter to see f it's dropped and fell asleep... if unplug the other side and reobserve. MAKE SURE not to unlock the vehicle or set the alarm off or the meter will go boom. might. I like to install a fuse on one the + side with a 10a fuse so if you trigger the alarm or mess up it'll pop the fuse not the meter..

    MAKE SURE ONCE AGAIN:
    DONT set the alarm off while the meter is in line
    Don't plug the module back in after you've unplugged it it'll wake the entire car up and pop the DVOM
    observe between unplugs.. and then unplug that module after setting the seat in a good spot...
    or if you'd like I have a few 203 seat modules that are good as new. I keep them in stock since their really common. or were at least
     
  4. dave

    Dave New Member

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  5. CINELLImotorsports

    CINELLImotorsports New Member

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    Or find a schematic of the the plug on the module and put circuit 30 pin to a 87 circuit instead. If you look at the huge plug that connects to it it's really not difficult to get a testlight and see where your hots are
     
  6. pmosi

    pmosi New Member

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    Mercedes C320 seat motor draining battery

    I have a 2002 C320. Something in the car was draining my battery over night. After diagnosing the problem at the MB dealership, I was told that the power seat motor is draining the battery. Both seats. Come to find out that many other people have experienced the same problem.

    I called Mercedes USA and they said that since the car is out of warranty, there is not much they can do. But if enough people call and tell them that they have this same problem, they will realize that this is a defective part and they will issue a recall and pay for necessary repairs.

    Please call Mercedes USA and report this problem. 1-800-FOR-MERCEDES (1-800-367-6372) or 201-476-6200
     
  7. CINELLImotorsports

    CINELLImotorsports New Member

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    This has been an issue for years now. There not going to do anything about it.
     
  8. Dennis Anttila

    Dennis Anttila New Member

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    2002 Mercedes C240 battery goes dead in 2 weeks

    I am helping out a friend to solve this problem. The car seat module was changed out and very expensive. A new battery was installed 2 weeks ago and now it reads 1.2 Volt. It's toast!
    I hooked up a small 12 volt battery with a calibrated amp meter in series. The reading was 200ma, sometimes 125ma. I unplugged both seat modules - still 200ma. I turn on the parking lights and the current goes to 4 amps. When I turn off the lights the current drops immediately to 500ma then to 200ma. I checked all the door and trunk switches. When any switch is changed (on - off) the current rises to the draw of the lamp and slowly fades down to 200ma when off. At this point the electronics are active as a warning message was displayed when the parking lights were on. Turn off the lights and the screen goes dark. Makes sense. So far I have only removed 2 of the high amp fuses as I need some needle nose pliers to remove the small ones. Getting the relays out is a pain and I need a "mini hook" to assist me. Anyway my theory is the light/whatever control module has a shorted relay driver. I hope to see the current go to the micro-amps or maybe a couple of milli-amps when solved.

    That 200ma load x 24 hours x 14 days is 67.2 ampere hours consumed. In the real world the battery load would decrease as the terminal drops to 1 volt! Has anyone got any additional clues and am I on the right track or just blowing smoke?
    Thanks all.
     
  9. CINELLImotorsports

    CINELLImotorsports New Member

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    In order to do a battery draw test the vehicle has to be able to be "put to sleep" so doors closed, alarm armed, everything off. Anything that sets the alarm off will wake the car back up and then you have to wait for it to go back to sleep again. IF you have a meeter hooked up a make sure to fuse the meter in line so that if the alarm is triggered then it will pop the fuse instead of your meter 200ma is still too much obviously. after locating the fuse you have to locate all the modules on the fuse and unplug them one by one... Try to dorr control moduels
     
  10. Dennis Anttila

    Dennis Anttila New Member

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    Thanks for the info. I am going to check the fuses one by one when I get home and on this weekend. I left the car idle with all the doors closed and waited 15 minutes. It will not go to sleep - a little restless. Maybe too much coffee. :) I did not set the alarm though. The meter I use is an analog meter 0 to 10 amps. .2 amps shows a reading of one division. I verified this with a digital meter and it read 200ma so the car running 10 times the standby current that it should be. I can turn on the parking lights and get a 4 amp indication. The headlamps peg the meter which is expected. Anyway I will investigate further to find the culprit. Again thanks and if I find something I will post it.
     
  11. Dennis Anttila

    Dennis Anttila New Member

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    Thanks so much. I took your advice and set the alarm (door locks). After about 15 minutes the current was so low I could not tell on the ammeter. So I slipped in the digital meter without breaking the connection. It was 19ma a more respectable amount. Then I hit the key fob blew the fuse in my meter. :-( I reinstalled the amp meter and retested. Waited about 15 minutes and the current was unreadable. So the moral of the story lock the car with alarm set it will start after several weeks of setting. Beyond that disconnect the battery and manual lock with a key for storage. This was an expensive lesson. Anyway all is well now.
     

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