quietcoolone

Hello,
My 2003 CLK500 has developed a 1.5A drain killing the battery. I have read much about it here and have narrowed it down to both driver and passenger seat control modules. -- yes both are drawing down the battery. (with both disconnected, battery voltage drops from 12.79 to 12.59 over a 12 hour span)
All seat controls work but CAN is staying alive. I'm wanting to fix this without having to pay for replacement modules.
Unlike the other fixes i've found which includes an ACC wire, my vehicle has only two (12V BAT and Ground) so swapping the 12V battery wire to the ACC wire is not an option unless i run a separate wire.
Observations/plan/questions:
1. If i disconnect the power plug and CAN plug, then reconnect only the CAN plug, current draw remains at 1.5A and does not drop until the CAN bus plug (x30/7) is disconnected
2. With module powered, the seat controls do not function if CAN plug is disconnected
Plan:
See attached picture/diagram which consist of one Channel DPDT Relay, a transistor, diode across the coil and resistor at the base of the transistor.
1. Cut both CAN wires 2 inches from the plug.
2. Run an ACC wire to the (IN) input which will trigger the relay contacts from NC to NO state and connect both the canL and canH from (M) module side to CanL and canH (C) on car side. (NC1 and NC2 are connected to to COM1 and COM2 when relay is its natural state)

Once ignition is turned on, relay circuit will switch to NO allowing signal to flow from module to car. Once ignition if off the circuit will go back to open circuit. By doing this i'm also hoping the seat memory feature will continue to work.
I have not tested the circuit in the car to see how much current it will draw, but if excessive i can always use the same ignition wire for power and trigger (in).
What are your thoughts?

Rudeney

This might help:

http://www.benzworld.org/forums/w203...ower-seat.html

quietcoolone

Thank you, but that fix was mentioned in the opening. That vehicle has 3 wires (ACC, BAT, Ground) my CLK500 has 2 (BAT and Ground).
I can also perform that mod if i ran a separate ACC wire to the seat, but my dilemma is how long does seat memory remain alive once power is removed from the module?
my proposed fix is to interrupt CAN so that module do not drain battery.
Will try my setup over the weekend.

quietcoolone

The circuit to turn can signal with ignition switch worked and drain dropped with seat module connected directly to battery they still draw a small amount of current which over time will draw down battery. To fix this problem i will have to replace the modules or resort to switch from battery power to ignition power.

Rudeney

I think the crux of the C-Class fix is to change the power from an always-on circuit to a switched circuit. That way, even if the seat controller does pull current erroneously, it won't do it with the ignition off.