Ok, so in fixing the drivers front seat today (lower RR track bolt missing) I put the seat back in full forward position. Now it is stuck there. I can hear the relay under the seat clicking, but no movement.

I removed the seat back cover, and also removed/looked at the position rheostat (?) but still no luck. What next?

The back had been working fine over the past couple of days. Lower seat functions as normal.

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But what do I know...

1984 300SD 256k

I have similar problems on the SD.

Sometimes the seat works.........sometimes it doesn't. My guess is that the seat switch is NG. Some folks have taken it out, completely disassembled it, and cleaned it. This has worked, but there are a bunch of little parts that wish to go airborne.

I purchased a new one..........but, haven't put it in yet.

Fixed it!

While the wife held the button backwards, I rapped on the frame next to the motor with a body hammer. As I suspected, the motor brushes were probably stuck. Regardless, it is working!

Disappointingly, the seat back frame has fatigue cracked at the lower point where the gear drive is. I suppose on the positive side, it looks like driver and passenger side seats and components are interchangeable.

On to the next problem...

__________________
But what do I know...

1984 300SD 256k

Don't be afraid of tackling the seat switches. There are a number of parts, but each of the switches is of a similar design, so once you understand one, you've got them all. The switch for the forward/rearward slide has a different pivot, but is otherwise like the others. Do be careful keeping the switch stalks where they belong--they will fit in "wrong" positions, but because of the offsets, the cover will not go on. Each side of each switch has a ball bearing/ spring and another ball bearing on top. You can use a dab of grease on the top ball bearing to hold it in place as you snap the cover back on.
Best advice is the screw down the switch down to a 2X4, or 2X6, or similar base, AFTER removing the screw from the backside. That keeps everything stable and much easier to work on.

I have done a bunch of rebuilds on these switches with no problem. Just take your time, Clean the contacts with a pencil eraser then use a little dialectric grease to hold parts in place while you put it all back together.

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1983 300SD
200000miles

don't forget to check your ground. My driver's seat always had intermittent problems, you could never tell when it would work (it usually didn't). When I replaced it with another completely different seat, I eliminated the door mounted seat controls entirely. Now, it usually operated but not always! The seat is grounded by a wire that travels into the door and then back out. Moving the wires around in the door would make it work or not. I grounded the seat near it's mounting points and haven't had a problem since.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Yep, there's lots of BB's in the switch. Be very careful when opening one. Best done over a box with a sheet of paper in it to catch the BB's. Otherwise you could spend many hours looking for them if they get loose on the garage floor.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

BTW other than seat belt and arm-rest the drivers and passenger seats are identical.

You will have to drill out some rivits to get the seat belt assembly off and the arm rest actually bolts on to the seat frame. Just take your time and get the back of the seat off first

I found a like new passenger seat in a w126 at a wrecking yard so I replaced the driver seat in my 300SD