The 2004 Mercedes is a great car and serves as my daily driver for commuting to work. However, the S430 is plagued by design flaw which can cause water to enter the interior of the car.
One morning as I was driving to work in my S430 and I randomly began to have electrical problems. I pulled over and shut the car off, after noticing my SRS flashing codes like Las Vegas. Generally speaking electrical problems are hell with cars, especially luxury vehicles.
So, I attempted to start the car after letting it sit a moment; and as luck would have it the car would no longer start. I got out and immediately noticed that my brake lights remained on. I doubled checked the switch and that wasn’t the problem. I then proceeded to unhook the battery in an attempt to save it. My trunk would not open, both key-less entry and via manual operation.
To make a long story short; while checking the passenger side fuse box I placed my hand on the floor board and it was soaking wet. I couldn’t recall driving in standing water or leaving my windows down.
In the end water had entered into the cabin via the A/C duct system. The problem is caused by the drainage plug getting clogged by debris in the A/C suction vent area. Once the water tops out it has no where else to go but to flow in to the A/C system.
Open the hood, and gently pull back the plastic covering. Using your finger push it through and feel for the plug at the bottom. Once you locate the plug, unclog it and push it all the way down to relieve the water.
Once water gets in, it often corrodes the electrical system. You will need to remove your rear seat and expose the rear SAM; that has all the fuses and check for corrosion. It may or may not be visible by just looking. Your Rear SAM may need to be replaced once it has corroded.
Common Symptoms of this problem:
Brake lights remain on.
Soft doors won’t work.
By Donzi M.