Drivers power seat control module questions and issues
 

I have a 2005 E500 4Matic wagon which has the Avantgarde package with heated seats and the dynamic seat option. Having some issues with the driver power seat not operating. I was guessing that it was likely going to be the seat control module because I could hear the faint click of what I assume is a relay from within the module when I attempted to adjust the steering wheel or seat. I could also feel the click when I placed my fingers on the body of the module, which confirmed it's source.

I was able to source another module for cheap locally as a quick easy gamble. I haven't had a chance to get outside and attempt swapping it out. The part number from my control module is 211 870 05 26. The part I picked up from local salvage yard is 211 820 85 85, which I believe came from a 2005 E320. Are these modules interchangable? If not, I can source another. I grabbed this one because it was so convenient. Confirmed working when removed as well.

Unfortunately, I'm tall and the seat is moved a little far back with the rear of the cushion tilted down in the back. That means I have zero chance of access to the two rear mounting screws of the seat. I'm dying to take it out and do some testing, but can't figure out a way to remove the seat without access to these rear fasteners. Anyone have any clever ideas on how to do this?

I can only test two things right now. I removed the power connection from the module and can confirm there is 12VDC power to it. Also, I have the iCarsoft MBII diagnostic tool. The passenger seat control module shows up in the diagnostic tool, but the drivers does not. Also, my "relay clicking sound" is gone now from the driver seat control module. Does anyone have any insight or ideas for this with the given information?

Could this be just a CAN Bus communication error and the module is still working? Are there any other things I can check? The switch is not the issue, I actually had a spare laying around, and the memory buttons still function which is confirmed by my mirrors still adjusting. All fuses are still good. I'm out of ideas and at the moment, I'm the only one who could drive the car due to it's adjusted distance for my long legs. Is the passenger seat control module able to be swapped to the drivers seat for process of elimination troubleshooting?

Thanks for your time.

Mercedes Module compatibility
 

mcduffmcduff,

I wish I had the answer for you however I am in a very similar situation. I use the website, www.mbpartsworld.com to check fitment of used parts I find on ebay and elsewhere. On that website it takes a bit of detective work but it appears your original module (211-870-05-26) was superseded by (211-870-40-85). On that same page it shows that (211-870-40-85) also superseded the new used part you got (211-820-85-85). So as far as compatibility, since both were replaced by the same module it is probably reasonable to assume they are compatible. However this is where it gets a bit weird. That same new part (211-870-40-85) that superseded both is listed that it "MAY" be compatible with your vehicle but if you want the exact new replacement you need to order (211-545-64-32). Unfortunately this new (211-545-64-32) part has no trace-ability back to either of the used part numbers you have now. Typical Mercedes parts madness.

The problem I'm having with my vehicle is that while I am fortunate that my seat still moves forward and back so I can remove it unfortunately the other movements are wacky. For example, the seat back will tilt back all the way then will tilt forward but always stops at the same point but is still leaning too far back to safely drive the car. Then the front seat bottom up/down control won't move at all but I do hear the same relay clicking that you mentioned. Also the headrest will not move at all. I have already swapped out the seat switch and got the exact same condition. I have also swapped out the control module with one that Mercedes says is compatible with my vehicle but this one doesn't move the seat at all in any direction and there are no more relay clicking sounds.

My question is, do these control modules require re-programming to your specific vehicle even though they are compatible?

Thanks,

Brian

Guys, it may not be the module. On my W210 it was the switch assembly in the door. I'd push the button to move the seat backwards and it would move forward. I'd then pull the button to move the seat backwards and it would move forward again. Seat back would not move to full back or full forward. Seat height/tilt adjustment was malfunctioning. I replaced the switch assembly in the door and all was well.

Worth a look.

bbirdwell,

I appreciate the response and the switch was my first thought so I purchased a known good switch and got the exact same movement from either switch so in my case it definitely isn't the switch. So then I moved onto the controller and that is where I am now.

Thanks, anyway,

Brian

I have a similar seat if my 05 CDI. There are two systems in your seat. The motors are controlled by the module on the bottom of the seat and the air bladders (bolsters, lumbar and cushion length adjuster) are a different module with air valves and pressure sensors. Every movement is a software command sent to the seat via a digital bus (CAN) command. To move the seat: Door switch sends command to door module, door module broadcasts command on bus that seat controller recognizes and reacts to. I have an inexpensive analyzer made by iCarsoft. The cost on Amazon was about $150. With that I can scan every module for faults and watch switch closure events. Your issue could be a failed seat motor and not the module. On my car the only feature that isn't working properly is the seat vent feature. My car is reporting intermittent communication issues which could be connection or module related. Since it's only the vent, it hasn't made it high on my list yet.

I have since bought another seat control module that has a matching part number that is a confirmed working unit. It was not the source of my problem. I also have the iCarSoft MBII diagnostic tool. The driver seat control module does not show up in the diagnostic tool, but the passenger seat does. I have also confirmed that the driver seat control module does have 12VDC power.

I have a feeling my problem may be the CAN Bus connection underneath the LF floor/carpet. I'm going to investigate hopefully within the next few days time. I'm expecting to find some form of corrosion or deterioration on the CAN Bus connector/hub there. I forgot it was under there and I hadn't considered any correlation with my seat problem and a previous water ingress issue caused by a clogged sunroof drain that wet the door sill area where I believe this connector is approximately located.

I'll definitely report back with my findings.

Sounds like you are on the right track. The driver's side seat control module N32/1 connects to the CAN bus connector X30/7 on the driver's side under the door sill. The passenger seat control module N32/2 connects to the CAN bus connector X30/4 in the passenger side footwell. Be aware the CAN C connector X30/5 is also in the driver's side rocker panel. It will have light-colored wires while the X30/7 CAN B connector for the seat will have the dark-colored wires.
You are going to have to lift the door weatherstripping, pop the door sill off, then you can lift the carpet and open the wiring trough.

Please update any solution.

I have successfully located and repaired my problem, and my driver's power seat and steering wheel adjustment now work as expected.

The issue was caused by an older water ingress problem at the LF door sill area. It was fixed a long time ago, but I forgot to consider it when thinking about power seat issues. The sunroof drain clogged itself a while ago. Water was traveling down the A pillar, behind it's interior trim, and down to the LF door sill, and under the LF floor/carpet. Along the left door sill is one of the W211's main cable transit paths. It's semi enclosed in a plastic box with a lid. There's a lot of wire in there.

My main issue was a pretty thick, lower gauge wire (probably about an 8 gauge) that somehow corroded and was basically almost severed due to this corrosion and deterioration. The outer jacket must have been compromised somehow, because I can't really imagine any other reason for for it to corrode and fall apart in the middle of itself. The wire was a red wire with a yellow stripe. Due to it's lower gauge, I'd have to imagine it's handling a higher amperage load. I didn't have much time to investigate after my repair, so I don't actually know where it's source and destination is. If I had to guess, I figure it might go to the Rear SAM. I'll look into that in the near future when I take the car apart again.

I took a couple of quick photos before the repair, and I'll attach one to this post. wasn't really much to see.

There was some light surface rust on the floor board here and there that I scraped away, cleaned up, and treated. I'll be revisiting that in the near future. This particular wire had enough slack on it, so I didn't have to bridge it with another piece of wire. I didn't have to cut it back too much on either side. The corrosion didn't go too far under the outer jacket, maybe about a 1/4" on each end. Before I reconnected the wire, I slid a couple pieces of appropriately sized heat shrink on there to be doubled up, made my repair, and everything works great. Driver seat control module shows up in the diagnostic tool as well.

I didn't see any other issues while looking around. No other compromised outer jackets or corrosion. Well, there was one green wire that looked a little questionable, but I inspected it and it should be fine. Outer jacket had a little nick in it, but I took care of that as well. I'm sure it won't be my last visit to this area though.




https://cimg5.ibsrv.net/gimg/www.mbw...27015510d.jpeg

I submitted a reply with the solution to my problem about 12 or so hours ago. Apparently, because it contained 1 picture, it requires moderator approval. Not sure if 12 or more hours is typical for turnaround time on this, but in case it doesn’t go through, I wanted to post a shortened version.

I fixed my seat and it was a wire.