I own a 2000 S320 which I love to drive, but it has given me trouble from the start. (DMV called the Cops when I tried to register it, Cops seized the car, took me a week and a lot of phone calls to get it back. Bought it at an official MB dealer, so wouldn't have expected that. Plus technical issues every 2 or 3 months, but so far I was always able to get it fixed.)

Some weeks ago then the battery was always drained over night and one evening while driving the back lights went apesh*t. Reversing lights were on while driving 130 on the Autobahn, brake lights made a little light show, 3rd brake light was on constantly. I also had no wiper control anymore, windwos didn't work, I couldn't switch off the front light, no turn signals etc.

I then found out that there was water under the backseats and the SAM had suffered severely. I took it out, opened it, cleaned it thoroughly, reinstalled it. Windows etc. started working again, however the back lights kept on having problems: 3rd brake light still on constantly (even when engine is off and car locked), right brake light won't work. I also got an error message for the faulty brake lights. I bought a new (used) SAM and installed it, however the back lights didn't work at all then, which seems to be due to that it needs to be programmed to the car.

I found a guy who could program it,but he said he needed the old one back in first to read it out. So put it back in. However when he connected his Star Diagnosis he could access all units except the SAM. We thought the SAM might be so broken that the SD can't "see" it anymore, but when we installed the new SAM, his SD also couldn't access that one. So I had to drive back home. (With the old SAM and funky brake lights). Later I realized that the car also had stopped giving me an error message for the faulty brake lights, the only error I get now is "display broken" (don't know how to translate it, I think it's trying to tell me that speedometer etc. don't work, but the only thing not working there seems to be the fuel gage). Also it doesn't beep anymore when I open the door with the lights switched on.

Is the fact that the SD couldn't connect to the SAM and that I don't get any error message for the broken brake lights somehow connected? Are there any specific cables I need to check for the connection to the SD? If I manage to get the error mesage for the faulty brake lights back, would that mean that the SD could also connect again?

Thanks in advance for your help and sorry for my bad english.

 

You replaced the SAM - but did you get rid of ALL the water? I'm serious - you got water there, but that likely means that there is water under the entire floor. Water that is corroding the SAM power supply, and CANBUS wiring in the various blocks under the carpet. Pull up all four carpets, and vacuum out the water, thoroughly dry out the carpets (it's not easy, you'll need to vacuum out the water from the foam backing, then let them sit outside in the sun for a day or two), then, and this is important, check each junction block for corrosion and clean them up. If you find corrosion in those blocks, you'll have to be certain that the connectors still work. Use De-Oxit electronic cleaner for mild cases of corrosion. You might have to replace some terminals. But until ALL the water is gone, you'll never get this cleared up...

 

Where is the water coming from? That's order of business #1. Check your COWL drain!

After that I would probably do what above poster suggested...

 

Yes, the cowl drain, or HVAC drain,for the HVAC plenum is the most likely cause for water under the floor and in the rear SAM.
Open the hood or bonnet.
Look at the right corner of the engine compartment and find the large grille cover. (Remember that on a vehicle, left and right are always defined as if you were sitting in the driver's seat. For example, the right headlight will be on your left as you stand in front of the car looking at it. Likewise, the right rear corner of the engine compartment is under the right corner of the windshield.)
Look down in through the grille, and find the lowest point of the funnel-shaped interior and find the hole that allows water to drain out of the container. If that hole gets even partially plugged with leaves or trash, water will collect in the area, and will eventually drain into the interior of the car under the carpets. You will not see this water, but it will gradually travel to the rear of the car and seriously damage the wiring and the rear SAM.
If you see no water in the plenum put the car where water that drains out will not hurt anything. Pour a couple of liters of water in through the grille into the plenum. The water must quickly drain away to the ground under the car. If the water does not quickly drain, carefully snap the plastic grille off of the plenum and clean the drain.
You must then remove the right carpets and dry them and all of the floor area completely. Otherwise, the water trapped in the floor and the foam carpet padding will continue to cause severe damage to the wiring and electronics, as well as rust.