Originally Posted by Western140

I have actually had a similar problem with my 1998 S420 (W140 body). Last winter I went through an automatic carwash in the morning, and then drove to work. When I left work to go to lunch, the climate control blower was running, even though the car was off and all locked up. It had obviously been running for quite a long time, because the battery was almost dead...the car barely started up. After I got home and turned the car off and took out the key, I only had to sit and wait for about 45 seconds before the fan turned itself on again. When I got my head up next to the air intake vent on the top of the hood, I could hear a gurgling and bubbling sound, like one of the sprayers in the car wash had somehow aimed itself just right (or wrong) for a few seconds and forced water into a spot that it shouldn't have gone inside the air supply plenum.

I had to drive to Oregon for a 4 day trip that night, and I noticed that the air conditioner was unable to effectively dehumidify the air inside the cabin during the 5 hour drive. When I got there, I was nervous about the fan draining my battery when my car sat undriven for 4 days, especially since I was out in a very remote small town (the fan went on after I turned off the car after the long trip). I tried to pull out fuses one by one, both from the underhood fuse box and the trunk fuse box, but the blower stayed on even after I had tried every fuse! I ended up having to disconnect the battery.

When I reconnected the battery and drove back to Seattle, the problem never returned. I assume that the water that had pooled up somewhere in the underhood air supply plenum had evaporated and eliminated some kind of short circuit.

Has anyone else had this problem occur before?