Mercedes-Benz W202 battery drains when parked
How large a standby current is allowed in a Mercedes-Benz W202?
Once the car has stood and its devices have gone to sleep, the standby current should be under 100 mA, typically 40–80 mA. With the alarm it can be about 85 mA. A clearly higher reading means that some device is drawing current continuously.
How do I find the cause of the Mercedes-Benz W202 battery draining?
1. Disconnect the battery earth lead and connect an ammeter between it and the battery negative terminal. 2. Read the current. 3. Remove fuses one at a time. When the reading drops close to zero, the fault is behind that fuse. 4. The fuse box cover or the owner's manual shows what the fuse feeds.
What usually drains a Mercedes-Benz W202 battery?
A faulty battery, for example with one cell broken, drains quickly without any other fault. Current is also leaked by a stereo wake-up wire connected to a permanent live, an antenna amplifier that is on all the time, and damp or oxidised connectors of the window control unit. Removing the fuse of the boot comfort box cuts off its current consumption.