Headlights and tailights on when switch in off, seats and windows don't work
Thread Starter
Member
Joined: Apr 2015
Posts: 222
Likes: 78
S-series 2003 S500 4matic
Headlights and tailights on when switch in off, seats and windows don't work
Working on a 2021 S550 that had water damage.
The headlights and taillights are lit when the car is turned on, even with the headlight switch turned to off. The windows won't go up or down, and the power seats will not move either. Sunroof is not moving either.
Ran SDS and states can't get to the front or rear sam. Tried to start the car, it clicks for a microsecond and then stops. Yesterday late in the afternoon was able to get the front driver side and passenger side window to roll down, but won't go up.
Installed a brand new battery, no change. Cleaned all the interior grounds, no change. The radio works just fine. Inspected the front SAM, no sign of any corrosion whatsoever. Replaced the central gateway, no change (also installed the pulled central gateway in a 2011 S550 and it functions fine. Cleaned the CAN connections thoroughly on the driver side of the interior. Currently can't get to the passenger side CAN bus, but no water in that area.
Currently stumped. Sense moisture is somewhere causing this, but can't find it. Yesterday, the windows did roll down late in the afternoon, heat of the day, maybe thinking moisture was reduced and allowed some current flow. Suspecting a weak ground... but no idea where.
Any thoughts?
The headlights and taillights are lit when the car is turned on, even with the headlight switch turned to off. The windows won't go up or down, and the power seats will not move either. Sunroof is not moving either.
Ran SDS and states can't get to the front or rear sam. Tried to start the car, it clicks for a microsecond and then stops. Yesterday late in the afternoon was able to get the front driver side and passenger side window to roll down, but won't go up.
Installed a brand new battery, no change. Cleaned all the interior grounds, no change. The radio works just fine. Inspected the front SAM, no sign of any corrosion whatsoever. Replaced the central gateway, no change (also installed the pulled central gateway in a 2011 S550 and it functions fine. Cleaned the CAN connections thoroughly on the driver side of the interior. Currently can't get to the passenger side CAN bus, but no water in that area.
Currently stumped. Sense moisture is somewhere causing this, but can't find it. Yesterday, the windows did roll down late in the afternoon, heat of the day, maybe thinking moisture was reduced and allowed some current flow. Suspecting a weak ground... but no idea where.
Any thoughts?
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Joined: Sep 2005
Posts: 6,189
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From: Albuquerque
'10 CL550, '12 GL550
Your problem reads like the classic wet SAM. Replacement may be more likely than repair.
http://www.mercedesmedic.com/mercedes-sam-module/
http://www.mercedesmedic.com/mercedes-sam-module/
Thread Starter
Member
Joined: Apr 2015
Posts: 222
Likes: 78
S-series 2003 S500 4matic
Chris,
Thanks for the reply. I have inspected the SAM and connected fuse box. Both are spotless and show zero sign of water.
Right now all indications is pointing to a LIN BUS issue. Research indicates all the issues the car is having are all connected to the LIN BUS. Read on another forum of major LIN BUS disruptions for this very simple and crewed device "Mercedes-Benz OE 2218301246 - Right HVAC Duct Adapter". How a tiny dumb device simply disconnect from the LIN BUS can take out turn signals, headlights, climate control, etc... is well beyond anything I can imagine. But checking into things any device connected to the LIN BUS that has a issue can take out all the devices on the LIN BUS....
Thread Starter
Member
Joined: Apr 2015
Posts: 222
Likes: 78
S-series 2003 S500 4matic
lkchris,
You were right.
Car is now running, likely fully operational. I need to put the interior back together.
I decided not to replace the front SAM (computer) as it was spotless and had zero signs of water or any other damage. I spent about 25 hours troubleshooting the interior LIN and CAN BUSs. I was unable to isolate the issue, so for the heck of it I replaced the front SAM.
BINGO. Everything working just fine.
Next step is to put the interior back together.
Much easier job than the white S550 which still need a lot of attention.
You were right.
Car is now running, likely fully operational. I need to put the interior back together.
I decided not to replace the front SAM (computer) as it was spotless and had zero signs of water or any other damage. I spent about 25 hours troubleshooting the interior LIN and CAN BUSs. I was unable to isolate the issue, so for the heck of it I replaced the front SAM.
BINGO. Everything working just fine.
Next step is to put the interior back together.
Much easier job than the white S550 which still need a lot of attention.
