checking electrical drain when car turned off on 2001 Mercedes-Benz C320

My battery (new) has to be jumped about every day. My passenger seat module was unplugged some time ago by dealer saying it was draining while car was off. How can I determine the drainage source? The passenger door window does not work any longer and the lock sounds like it is unlocking / locking twice when engaged. The door panel lights indicating window and memory button were flashing but now are off totally.

by in Huntsville, AL on December 13, 2010
1 answer 4 comments
ANSWER by on December 14, 2010
Early 2000 models has many problems with the Seat Control Modules. They won't go to sleep mode and drains 1.2 amps continuously. You have 2 choice: 1, replace the module (it has to be programmed with an OE computer), that's the more expensive repair 2, find a good tech with electrical experience and ask him to install a relay to the seat module, which activated by the cigarette lighter's power source. This way the power will be cut off from the seat controller when you remove the ignition key so the module won't drains the battery and you can adjust your seat. Zee
COMMENT by on December 14, 2010
Thank you very much for the tip! Will the seat module effect other electrical issues? I noticed my blower motor on the heat/AC won't come on some times - I thought the sensor was waiting until the engine heated sufficiently but many times I notice it won't turn on at all...even when I push max speed. Also, I noticed the passenger door buttons (lights in the memory button and the window button) began to flash on / off. Now they don't light at all. The door lock on the front passenger door operates but acts like it double clicks when the lock or unlock button is activated. The window was jumping up and down when it was activated but now it doesn't function at all. Many times I get a "check R break light, running on substitute" error - but the bulb is burning. After a while or if I turn the car off and back on without the lights on, it stops. Are all these issues related to a sensor or computer feed? Thanks! Not sure where to start.
COMMENT by on December 14, 2010
If there are electrical problems in different systems I'd check / clean ground connections first. There is a rear relay box in the trunk, I'd check the connections there also. Pay attention of the electrical harness connections, make sure the connecting pins are clean and oxidation free. Sometimes better to use a good light source and a magnifying glass. Before you start to disconnect and clean electrical connections and components, make sure the negative battery cable is disconnected! Zee
COMMENT by on December 14, 2010
Thanks Zee! You're right on top of your game it seems! Do you know of a source where I might get photos or images of the areas / components you're refering to ? Thanks a million! Doug
COMMENT by on December 14, 2010
You can find great repair manuals with step-by-step instructions, diagrams, parts locations and other important information here: Zee

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