1987 420SEL power seat doesn't work
 

None of the adjustments on the front passenger seat of my 420SEL are working except the seat up/down and the headrest. The seat back is stuck in the reclined position.

My car has the memory seats which have adjustment switches on the door panels.

[later edit]: You might want to skip to the last post in this thread.

I've searched for a thread covering this, but didn't find anything. Can anybody refer me to one, maybe?

Or, where can I get the theory of operation and a schematic diagram of the power seat circuit? Would anyone have any troubleshooting and repair tips? Does the power seat relay go bad? How about the door switches? And does the door have to be open in order to adjust the seat?

Any help or suggestions would be appreciated. Thanks.

- retro

a mistake in my earlier post
 

It does have memory seats. I didn't realize that when I first posted.

Ever replace the fuses? Old ones hamper the electrical system of this car over time......

hitmanx, doesn't the fact that it is happening only on one side rule out the fuses, since I think both seat motors get their supply lines from the same fuse?

Please correct me if I am wrong, but I thought that's how I read the schematic.

I removed and inspected the old door panel switch. It looked lousy, so I am going to replace it first.

Let me know if you have any other suggestions.

That seat was out of the car for re-upholstery recently. I wonder if the upholstery shop didn't plug the recline motor back in?

The seat went back, and now it will not go forward?

Lots of things are in an X-circuit, such as RF and LR window on one... and LF and RR on another.

It's worth checking as it's easy and simple.

BTDT

iwrock wrote: "The seat went back, and now it will not go forward?"

Yes.

probably a bad switch
 

sounds to me like its a bad switch. same thing happened to my car. the recliner and headrest wouldn't work. i took the panel off and messed with the switch and was able to temporarily move the seats into a comfortable position. but my indie told me its a bad switch. ill get it replaced eventually.


so i would check there

Clean out the switch. With age some contacts will corrode and you'll get some gremlins. Follow the below procedure and clean out all the contacts. I've done this once a year to my dad's 300TD and have cleaned out my coupes.

Here's a DIY: http://www.peachparts.com/Wikka/W124SeatSwitch

My car does have the memory seats. The old switch didn't look good to me, so I replaced it with a new one, but I still have the same problem.

Actually, the seat up/down adjustment does work, and so does the head restraint adjustment, but none of the other adjustments work. I can hear the motor trying to actuate with the other adjustments, but it doesn't move anything. I have the seat removed from the body and would like to put it on the test bench, but I'm having problems figuring out how to disconnect the two wires from the floor harness to the seat adjustment mechanism. It looks like you need to remove a plastic cover before you can unlock the connectors, but how do you remove the cover?

Then I need to figure out how the mechanism and motors is supposed to work. Can anybody give me a crash course on that?

Thanks!