I've got a 92' 400SE in which the passenger's front seat suddenly stopped responding to the controls. From what I have seen so far, there are no other electronic components that are having problems...which leads me to believe it is not a simple fuse. Also when I checked the fuses seemed fine. I removed the switches on the doors and checking the design I reverse wired the driver's side on the passenger's to see if it was the switch...no change. So put everything back and driver's side still works fine, while passenger's side is still bad. I did some basic checks on the wiring to the seat and it appears to be getting some power. I am down to considering two components...possibly a bad relay or the controller brain under the seat. I don't know where to find if there is a specific relay for the front passenger's seat so any help would be appreciated. While the controller brain under the seat is not very accessable due to the position that the seat is stuck in. Any experience and suggestions would be GREATLY APPRECIATED! Thanks.

These seats can be a real pain to fix when they suddenly stop in a bad location.

The controller boxes are identical left-to-right (I have '92 300SE). If you can get the seat out, swap the boxes and see if the problem goes away.

According to AllData, if you can move the seat cushion forward far enough (not the seat itself, just the lower cushion), you can get at the two front screws that hold the cushion to the frame. Remove those, and you can lift the seat cushion at the front, exposing the mechanics below. Once you're there, you can remove the controller unit. However, if the controller unit is dead like mine was, nothing works and if the screws aren't visible, you're toast. Even if they are, getting the inboard screw out is a true PITA.

I was lucky in that the position of the seat was such that I could get at all of the mounting screws to pull the seat out of the car.

I got REAL lucky and found a replacement part in a junkyard in Ohio by actually googling the part #! I got the sucker for $100 shipped and my problems are solved. I'm thinking about sending the original control to Programa (www.programainc.com) in Florida to see if they can diagnose/rebuild it. I got my CC unit rebuilt there and have been very satisfied with the results/cost.

It's not a lot of work to get the seats out when you can get access to the bolts. I found on my car (the passenger side had died) that the PO (or his simple-minded mechanic) had disconnected the plug for the motor that moves the seat front-to-back in order to use a 12v source to position the seat. I don't remember which motor it is, but if you can get the plug loose from the controller, 12v+ to one pin and 12v- to the other moves it one way - reverse the wires for the other direction. Be SURE to put the power to the right pins - I think there are 3 or more - one is for the rheostat which tells the controller where the seat is. I think the outer pair are the power to the motor.

I've seen a few of these parts on e-bay over the last few weeks. The cost at the dealer is outrageous (I think $500+), so that may be your best bet.

Dear wbrian63 thank you very much for your suggestions, I did look under the seat and unfortunately it froze in a position that makes everything difficult to get to. The control unit under the seat was definately one of my considerations of where the problem was however I was hesitant on just buying one (even used) to replace it until I had the opportunity to better diagnose the problem.

Question....on yours did ALL the power go out for the seat. On mine everything is out except the little dial on the side, which if I recall correctly is for lumbar. When I move the dial on the side of the seat you hear something going on....that is all that works.

Since I was not sure how the wiring was set up, I was thinking maybe a relay or fuse could be the source of my problem. I plan to check into things again this week and I'll see how possible it is to jump the motor and hopefully switch the units from the driver's and passenger's side to test things. Thanks again for your time and suggestions!!! All help is greatly appreciated!