W169 A150 Classic SE Electrical Power Drain

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New Member
Aug 21, 2021
Dartford Kent
W169 MB A150 Classic
This may apply to B Class and other types with a similar bulk head layout. I have previously gone through at least 3 batteries due to an unknown source causing a POWER DRAIN. However, these occurred generally after a lot of rain. I made a discovery that I believe may have stopped the power drain issue and this may be of help to others. I checked the pollen filter, sighted within the engine bay of the W169 near to the wiper housing on the front bulk head. The recess to which was full of water with the filter soaked as a consequence. Further, this little pool was dripping into the cabin and within its path was soaking the SAM unit located cabin side on the nearside (UK passenger side) of the W169. Further again, it was running toward the back of the car and ponding in the rear spare wheel well, I understand. Along this path various electrical components were affected: the seat belt junctions and I believe, the circuit board to the phone mount. The cure was simple. The drainage scuttle found below the pollen filter was blocked. Using a coat hanger I prodded out the blockage. This cleared a significant amount of putrid water which then drained normally through its designated channel onto the road. Managing to start the car using jump leads I ran the vehicle at idle for 1 and a half hours, with the heater at max and blowers cycling through the different venting positions. For now, the issue looks to be fixed. I post this as a help to others who face the same issue. Additionally, the symptoms I noticed - the mesh panel at the front of the W169 on the upper dash was rusty (had been since I bought the car 2 years ago), the interior windows were misted inside and the vehicle smelled musty.

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