Power Seat Anomaly
01-11-2011, 11:47 AM
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300SD 1982
Power Seat Anomaly
I just purchased a 1989 300 SEL
Weird thing with the seats.
Seats operate with the door open and keys out. Some functions are iffy (memory)
However, with the doors close and ignition on, the seat controls are dead. No adjustment, either side.
I know there is a feature to adjust the seats with the door open and I'm assuming there's some relay that makes that possible.
Any ideas what could cause this to happen?
Thanks,
Tim
Weird thing with the seats.
Seats operate with the door open and keys out. Some functions are iffy (memory)
However, with the doors close and ignition on, the seat controls are dead. No adjustment, either side.
I know there is a feature to adjust the seats with the door open and I'm assuming there's some relay that makes that possible.
Any ideas what could cause this to happen?
Thanks,
Tim
01-15-2011, 02:22 PM
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Join Date: Apr 2002
Location: Perth, Australia
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W124 230TE, W123 280E
Hi Tim,
The comfort system is what allows you to operate the windows and seats with the door open. From memory there's some changes in the way the memory works depending on when you use it. For example, with the door open and the key out, pressing one memory button briefly starts the seat moving and it will continue moving to the memory position without you holding the button down. However, with the ignition on and the door closed you need to hold the memory button until the seat has moved to it's final position. I guess it assumes there is someone in the seat and therefore could be dangerous for the driver to not have control of seat movement.
Anyway, there is a diode in the fuse box that is something to do with the comfort system. If the diode is kaput, then some odd things can happen with the system. I suspect this may be your problem.
In the fuse box there is a small black plastic dongle-looking thing, that connects into the fuse box with two electrical pins. When you remove the dongle, you can open the top of it to see a standard shape diode. You can replace the part yourself with a soldering iron and a replacement diode from an electronics hobby store, which beats paying an MB dealer an exorbitant amount of money for such a simple object.
Good luck with this since it's been a while since I've looked in a W126 fuse box.
The comfort system is what allows you to operate the windows and seats with the door open. From memory there's some changes in the way the memory works depending on when you use it. For example, with the door open and the key out, pressing one memory button briefly starts the seat moving and it will continue moving to the memory position without you holding the button down. However, with the ignition on and the door closed you need to hold the memory button until the seat has moved to it's final position. I guess it assumes there is someone in the seat and therefore could be dangerous for the driver to not have control of seat movement.
Anyway, there is a diode in the fuse box that is something to do with the comfort system. If the diode is kaput, then some odd things can happen with the system. I suspect this may be your problem.
In the fuse box there is a small black plastic dongle-looking thing, that connects into the fuse box with two electrical pins. When you remove the dongle, you can open the top of it to see a standard shape diode. You can replace the part yourself with a soldering iron and a replacement diode from an electronics hobby store, which beats paying an MB dealer an exorbitant amount of money for such a simple object.
Good luck with this since it's been a while since I've looked in a W126 fuse box.
