W126 Power Seat Motors - PeachParts Mercedes-Benz Forum

tinypanzer · #1 10-27-2009, 09:45 PM

Hello all......

My 560SEL has everything working except the tilt adjustment for the driver's seat. Of course, it's stuck in a nearly undrivable position.

I've got the back off the seat, but I cannot figure out how to get the motor out. Any suggestions?

Thanks!

tinypanzer · #2 10-28-2009, 06:25 PM

^bump^

Anyone?

Rob Pruijt · #3 10-28-2009, 07:30 PM

The seats don’t have a tilt adjustment, the front and rear height have separate motors.
The motors are under the seat (remove the 4 bolds and tilt seat backwards).
Most likely the switch in the door is not working.

Rob

tinypanzer · #4 10-28-2009, 10:24 PM

I'm referring to the seat back tilt, which the car definitely has.

I already know it's not the switch because I can hear the relay activating under the seat. My suspicion is that the motor is seized up.

If your sitting in the back seat, and you take the back off the driver's seat, it's the motor on the lower right - near the seat back pivot.

Thanks!

tinypanzer · #5 10-29-2009, 03:45 PM

Seriously? Nobody knows?

brainlair · #6 10-29-2009, 07:50 PM

Have you tried applying power directly to the motor? From what i've heard, the motors are reasonably reliable.

If I were you, I'd pull the seat from the car to get access to all the connectors underneath and try applying voltage to the connector at the end of the cable that comes directly from the motor. If it doesn't work, you'll just have to disassemble the seat until you have access to the bolts/screws that hold the motor in.

It sounds like you already have the backrest cover off, so the next thing i'd do is remove the backrest from the seat bottom-

http://i284.photobucket.com/albums/ll4/pwogaman/1985%20Mercedes%20300SD/100_2172.jpg

...But I suspect you'll need to go further, and remove the vinyl/leather seat back from the frame. I've never done that before, but will be soon because i'm replacing the vinyl on my driver's seat.

If it does prove to be the motor that doesn't work, you need to get another motor from another seat, so you might as well just find a working seat in the boneyard and swap your seat cover on to a seat back with a working motor in it. At least, that's what I'd do. Good luck!

retroguybilly · #7 10-29-2009, 07:53 PM

Does the recline motor run when you push the recline switch in either direction? If so, then the ratcheting-engagement mechanism where the seat back meets the seat bottom is broken. That mechansim has to engage in order to move the seat back upright, and it is not engaging. New ratcheter mechanisms are expensive ($200 or more from the dealer), and expensive and difficult to install because hardened rivets must be drilled out in order to separate the seat bottom from the seat back in order to replace the ratcheter (M-B riveted them together because they're a safety issue).

My best suggestion is to go to the salvage yard and buy another seat. They're pretty cheap. Mix, match and swap the parts from the salvage yard seat and your present seat until you've got a complete seat where everything works.

Another approach, if the recline motor runs but the ratcheter is broken, is to run the recline motor in the "upright" direction as you push forward hard on the seat back. The seat back will seem like it doesn't want to move upright, but if you push hard enough it will. Don't worry about breaking the ratcheter in such a case because it is already broken. When the seat back reaches the angle you desire, leave it there and either avoid pushing the recline button thereafter, or disconnect the power connector from the recline motor so somebody won't inadvertently recline it again.

tinypanzer · #8 10-30-2009, 05:28 PM

Thanks for the replies.

Yeah, the motor won't run in either direction even though I can hear the relay clicking over. I guess I'll but a drill battery on it directly and see if it will budge. I just assumed that the motor's dead because everything's plugged in and I can hear the relay working.....

The mechanism seems to be okay from what I can see, but I just can't get the motor to spin.

Thanks for the links. I'll let you know how it goes.

RPM55 · #9 10-30-2009, 06:54 PM

It's very possible that you have a bad memory control unit ( the part you are referring to as the relay ). Actually it probably is a bad relay inside the control unit. What you should do is what was suggested earlier, unplug the harness for that motor from the control unit and apply 12volts to see if the motor runs. If the motor runs then your control unit is likely bad.

tinypanzer · #10 10-30-2009, 09:18 PM

Thanks for the tip. I am going to try that and report back. I actually wasn't referring to the memory control unit per se, I was referring to what I could audibly tell was a relay of some sort. Perhaps the contacts are toast, or the memory unit has bad solder joints. Either way, it looks like I'm going diggin'

Frankly, I am quite comfortable with electronics and I'd almost prefer the problem to be a control box or relay rather than the motor!

Thanks again!

tinypanzer · #11 12-07-2009, 08:31 PM

Well, I solved the problem over the weekend.

This is an odd one, I really wish I had taken pictures.

Here's what happened - at some point, one of the springs in seat snapped. I guess the previous owner was hefty. Anyhow, the broken spring, the second from the rear underneath the seat, now had an exposed sharp metal edge on it. After repeated getting in and out of the car, the broken spring actually cut through the wire tail going to the seat tilt motor, severing 3 out of the 5 wires completely, and removing some insulation off the remaining two.

I had to unbolt the seat from the floor, but luckily did not have to remove it completely. I am skinny enough to contort myself upside down and underneath the thing when it is unbolted, and after some rather tricky splicing, soldering, and shrink-wrapping, I was able to make a very professional repair without even adding any wire, which was a miracle. MB gave us a good 10" of slack on that tail, and it was very useful indeed. There was even enough slack leftover to reroute the wire away from its previous position under Damocles' sword and to a safer spot.

Y'know those plastic thingies that you cut to length and then insert in a hole in a concrete wall to hold a screw? One of those worked perfectly to cover the broken spring end.

Everything works great now, except for some reason the seat makes a shuddering noise if you slide it rearwards while sitting in it. Hmmmmm......