hak-man

My 2004 Mercedes S430/W220 got wet the trunk opened up by it self over night and water made it down under the back seat. Since then my brake lights come on as soon as I start on the engine and will not go off until i turn off the ignition. So far i have changed the brake switch and fuse with rear sam still nothing. Any solution?. Appreciate it.

Thanks
Hak-Man.

Astro14

IF water got under the back seat, you're going to see more, and worse, problems until you get the rear SAM dried out and taken care of. Your problem right now is that water is still in the SAM, shorting out the brake light relay.

Remove the rear seat, vacuum up all the water, dry it out.

Disconnect the battery.

Remove the SAM itself, clean the contacts with a good contact cleaner like "Deoxit".

Reconnect the battery. Do the resets from your owners manual for windows and steering angle sensor.

Remove the carpet on the passenger side, take up the foam insulation underneath. Vacuum up the water in the wire conduit under the front seat. Put the carpet and insulation in the sun for a few days until it is bone dry.

You must do all of this, or corrosion and electrical shorts will cause numerous future problems.

wallyp

The usual two approaches are:
Remove, disassemble, and clean the rear SAM, drying it thoroughly and removing all corrosion.
Replace the rear SAM with an exact duplicate, then reprogramming it with the same options as the original.

hak-man

Ok my people. I did everything that was asked. All my Sam FL/FR/RR are dry and operational. Cuz none of them showing any active codes. But my brake lights are still staying ON. Can't shut them no matter what. Oh also my brake light assembly are also brand new and there is no corrosion. So what's NEXT?

I really appreciate your help.