E220 Cabriolet (A124) Parasitic drain ?

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CRJ343

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Joined
Jul 28, 2007
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51
Car
E220 Cabriolet
I have a late (1996) E220 cabriolet.
I had been experiencing a flat battery for the last couple of months which I put down to a 5 year old battery so I replaced it with a new one.
It was almost completely flatterned after 7 days of no use and returning from a 150 mile round trip.
In testing with a meter I am getting an 80ma "draw" with everything off.
Tried pulling each fuse one by one and and got a negligble drop (probably the radio anti-theft light).
Is this "normal" drain for my vehicle ?
 
80mA does sound a little high to me. I have not read up on the 124 era of car, but for later cars - like my S211 with more CAN network and electronic modules - Mercedes state 40mA max within 30 minutes of ignition off. In practice, my car draw drops to around 35mA a couple of minutes after being locked.

Our cars often have multiple fuse boxes, typically one in the engine bay, one in the boot, and W/S211 has a third in the dashboard. Not sure if yours is the same, but worth checking you are pulling them all as part of diagnosis. 80mA on a 12V battery is 0.96W, which sounds too small for a bulb staying on, so maybe an electronic module (what modules are on a 124, seat memory, roof, climate control?) staying awake.

Also worth noting that 80mA over 7 days is 13.44Ah, which should be well within the capacity of a healthy car battery without causing starting problems, certainly not 'almost completely flattened'. I wonder if there is a separate problem with your alternator that means the battery is never being properly charged.

Martin.
 
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