2002 C320 wagon
I'm having a problem with my battory drawing down over night.
After recharging the battory,I have performed the following tests.
I removed the negative battory cable and installed a voltmeter.
test-1
0.90MA draw and the the little circuit-board fan in the headliner dome lamp will continue to run.
test-2
0.90MA draw with the right seat module unpluged.
test-3
0.02MA draw with the right and left seat module unpluged,then the fan stop running.
test-4
0.90 MA draw with only the right seat module reconnected,and the little fan in the headliner starts to run?
Could I have 2 bad seat modules?
Thanks,any input

What is the exact build date of the car? The fan at the roof should be driven by the overhead control panel control unit. Perhaps it just starts when you connect the battery power and stops from a timer? In any case you should measure the quiescent current after some time only to ensure consumers have switched to sleep mode.

Having both front seat control modules go bad is fairly common. What happens is the seat control modules keep the CAN network awake, causing drain. You will need to wait atleast 5 minutes with key out, doors closed for CAN to go to sleep, or see if it even goes to sleep. You need to watch voltage direcly on CAN line bus. Where are you located? Your best bet is to find a good benz shop, to properly diagnose it, and if it needs seat module, it will have to be version coded anyways. You cant just plug it in.

Check out my diagnosis in the thread below. The issue was the driver's side seat control module. 0.90 mA is a normal draw. make sure its 0.90 mA and not 0.90 A (i.e. 900mA) cause that would be a problem

https://mbworld.org/forums/c-class-w203/216856-battery-problem.html

I have a reading of 0.90mA with the both left of right modules pluged in.Also the fan stays on in the head line at the headliner circuit board?
If I unplug both modules my reading drops down to 0.02mA.

If I replace both seat modules do they have to be reprogramed or are they self tuning?
Thanks for any support.

YOUR SEAT CONROL UNITS ARE ALREADY PROGRAMMED ,IT IS PLUG AND PLAY

The seat control modules have to be coded to the car for everything to work properly. Not just for seat movement, but coded for convenience features to work properly.