W126 Memory seats
 

I searched but most threads seem to just dead end with no actual results. Both my memory seats do not work. Buttons are not stuck and one set I recently cleaned. So I am pretty sure that with at least one its not the switches being sticky.

So how do they work? The seats operate fine (well except the passenger side which burns up the control board if forward/back is used for more than a second). Anyway. I press the green followed by a number within 3 seconds. Then I wait, adjust the seat and press a button (or hold a button down, manual is not clear) but nothing happens with either.

Do they have independent computers to control the memory function. And if so, is it the big black box under each? One of which I have repaired a few times :). And while I am on the topic, what the heck is the bright yellow box under the driver side blocking the under-seat vent?

I believe you need to hold the green button in to program a memory position.

-Jason

As in press a number then the green button? I am pretty sure the manual said green first, then a number. I will read it again though.

I have the manual but need to fly out. I will read it later and post what it says,

You press and hold the green button, then tap a number button.

FWIW 1991 cars have a different memory unit for the seats. It's more digital and should be more accurate.

-Jason

+1 on hold green in and touch memory number. By the way it will also adjust the steering wheel to saved position.

Ok. I will try that. I was just pressing the green button then pressing a number after letting off the green. I was not holding both or pressing both at the same time. I even read the manual and it just said to press the green button followed by a number.

Qute from manual
 

storing seat/ head restraint/steering wheel position in memory:

press green button and within 3 seconds press the program button 1 or 2 for that position

So doing as above, as I have been doing, does not work for either. Holding the green button down while pressing a number does also not work. Also, as I read somewhere, holding the number down until the seat finishes moving does nothing.

So it looks like, oddly, BOTH of my memory seat functions are out. Yet the seats operate.

Strange. Once the memory is programmed you have to hold the button in to make the items move to the remembered position. If you release the button they stop.

-Jason

Ya. Thats what I understood and so I tried holding he number instead of just pressing it - like more cars. Still nothing.

So maybe programming is working, but recalling is not. Just odd since the seats work find otherwise. Maybe I will have to take the doors apart and check the wiring. I found so many cut wires when I was installing the sounds system. They were from the PO doing a hack job in the sound system in the first place. I found wire clear cut and nicked bad. Just odd that all the controls work though.

And I did check to make sure all the connections under the seats were plugged in. Guess I will add it to my list of "really simple projects that turned out to be complicated".

It's never good when a hack tries to "upgrade" a car which has a 2 piece radio set....

-J

I own a 1991 560SEC and had the memory function of both seats stop working after a voltage surge. Try unplugging the translucent white relay in the fuse box for 5 minutes or so and plug it back in and try to reprogram. This worked for me. Mark

I will try. But they did not work before or after I pulled the battery.

My seats behaved like yours after I installed a rebuilt alternator. When I started the car for the first time there was a loud pop, huge electrical draw and burnt electrical smell. I checked to make sure I hadn't somehow botched the installation but everything was installed correctly. So I started the car again and everything except the seat memory worked fine including the alternator. I could adjust the seats by moving the switches but could not set the memory. I checked the fuse, etc. and found nothing wrong. I began looking on ebay for seat modules but based on price I purchased a used seat relay and installed it and the memory functions worked. Out of curiosity I reinstalled the old seat relay and the memory functions worked. Unfortunately, I did not try the memory functions immediately before replacing the relay with the good used unit. The seat relay for this vehicle appears to be much more than a relay with IC's, smd's, etc. and I assume it has some protective function for the control units similar to the OVP. The part number is 0015427819, it lists for about $56 and it looks like the attached. Mark

Thanks. I will look into the relay for sure. Not sure what else it could be anyway!

Pulled relay, nothing. Wonder if the relay is bad.

Ok. Does anybody know the location of the memory seat module? That is, is it separate from the seat computer? I ask because I found out a few things. One was a tip:

"-W126 fuse for trunk light and memory seats keeps blowing: the wiring harness near the trunk hinge flexes all the time, and the wires have shorted. Pull the wires and electrical tape them, and you'll be fine."

Why would the memory seats be dependent on trunk wiring? So i looked and found nothing in particular. But I did find a wiring harness along the body line that was taped to the antenna. When I removed it and pulled it apart I found four wires. Two were red with white stripe. Twisted together. Upon separation, trunk light went out. The other was a brown ground (cut and unattached) and the last was a light blue going nowhere.

But I am not sure where they would even go in the first place except to a module or plug. Especially odd is the trunk light. Why run a harness down then back up to the back of the seat then again to the trunk. And its a factory wrapped harness. So clearly there is a reason this is where it is. But no module, no connector and no clue whats up with the blue wire. Got no voltage off of it. Note: Stereo system was hacked to high heaven. Antenna wires were also wrapped up in this. They may have used this harness end for antenna power. Pic of hacked wire harness:

http://i135.photobucket.com/albums/q...6/IMG_0362.jpg

And then I also found this long ago. I am pretty sure that only one is in the car on the drivers side. Given that the harness seems to hide under the heat vent, I am not sure of there is an open harness on the passenger side. At one time that seat was disconnect and when I hooked it up in went into a loop. So it had issues which I sorta fixed (hooked up and works). But they may have removed this box to try to make the seat stop looping. Anyway, I took it off and apart. It has the same relays used in the seat control boxes. And everything is doubled up in pairs, so it may be the controller and it may control both seats. I am going to re-solder the board tonight and see if it helps. But it sure looks ok, no burnt stuff. Pics:

http://i135.photobucket.com/albums/q...6/IMG_0363.jpg
http://i135.photobucket.com/albums/q...6/IMG_0364.jpg


I guess at this point I am more curious about the blue wire and where it may have gone.

Yellow box appears to be for the heated seats. Crap.

The hacked wiring loom in the trunk is the original antenna wiring, blue is the antenna signal, the reds are power, and the brown ground.

The other box your hacking is the seat heater relay!

The memory seat controller has two parts, the larger box attached to the driver's seat motor frame and a smaller similar box under the passenger seat.

So, as I first thought long ago, the memory seating functionality is built into the same controllers that operate the seats? Makes me wonder even more as to why the memory seats dont work on both. One I can understand, but both with the rest of the functions being fine? Sorta odd. Then again I cant even get my vanity mirror lights to work, so I guess nothing can be too odd with this car.

The memory function will not work if either of the controllers is faulty.

I actually had the same thing happen to my 560 SEL. I had a short related to the anti-theft system. Anyhoo...I kept blowing the fuse that is responsible for among other things, the memory seat function. If you open your front drivers side door, the rear courtesy lamp (top rear middle of headliner) should come on. If it does not come on, then look at your fuses. I can't remember the fuse number ...i think it was #15 that kept blowing. Hope that helps.

As I said, they both work fine now unless there is something more wrong with them. Possible given that at one time they did not.

@ Cherry - Fuses look ok, but I thought the rear upper light only comes on when the back doors are open. I thought the lighting circuits are separate, as I was told. Although I swear when i first got the car the back did light up. As for anti-theft, that module is missing. Taken out, I presume, by the wonderful stereo installers of the pervious owner.

Wait, how could blue be signal when there is an actual antenna wire screwed into the antenna and then terminating at the amp/brain? And I see no blue wire on the antenna. Just a black, red, white.

From reading your posts it seemed that the memory functionality of store seat/steering wheel positions and then recalling and implementing those stored position was inoperative, perhaps I've mis-read the saga! If either memory controller is faulty the ability to store, recall, and reposition the seats and wheel is usually impaired. If your memory functionality is operative then most likely you have an intermittent problem and often times that is a wiring or grounding issue.

If they worked I would have not started this thread! :) But they way I read your original response was that if the seats did not function correctly (manually operate controls) then the memory would probably not work either. And thats the conundrum. Both seats operate fine with controls, but both lack memory functions. So I can adjust them all I like, I just can not get either to program to memory. Which, if its all one unit, is rather odd. Even more odd that both would fail since both seats are independent of each other.

Make sense and do you see why I am so confused on getting this repaired? If I has spares I could swap the controllers out. But I don't.

If they are indeed shot and no one has any more ideas, then I will have to go on the hunt and spend some cash on replacement controllers. Which is fine. I just prefer to exhaust all possible solutions for repair before replacement.

The antenna gets 12v power from the red wires, the blue wire is an antenna UP/DOWN signal wire from the head unit through the dash switch and back to the antenna. The blue wire tells the antenna circuitry to rise/retract/ partially or fully. The radio frequency signal is a larger coaxial cable which attaches directly to the connector which exits the antena staulk at an angle.

Mine have always come on when I open the front or back doors.

Thanks. I will check fuses again. Or as the tips suggest, just replace em all! Most are factory. But like I said, this issue was from day one.

Ok. So I am guessing there was, at one time, a connector which they, for whatever reason, removed and spiced some stuff together. Hence the lack of a blue wire on the antenna, it was probably the white one on the antenna that would have coupled with the blue.

Good to know actually since I have no radio at all right now due to the hack job. Thanks much!

Usually the original loom is chopped when an aftermarket replacement antenna is installed. In the factory install there is a 2X2 four pole female connector at the wire end which plugs onto a connector on the antenna.