w124 Cabrio passenger seat removal? - PeachParts Mercedes-Benz Forum

87tdwagen · #1 11-29-2018, 09:38 AM

Hello all:
After searching the forums and looking at my situation, I need some ideas as to how to remove the passenger seat in the 94 cabrio. I had a thread some years ago regarding the seat switch losing it's fore/aft function, and although that seemed to have worked itself out, it also has reared its ugly head again.

Currently the seat has all functions but the fore/aft one, unfortunately it is about 75% of the way forward and thus covers the front mounting bolts. The rears are accessible, but I cant get to the front ones to unbolt the seat. In the later w124 set-up the system uses micro switches and the switches are fine, and working as they should, so the loss of the fore/aft function seems to be either a motor or connection issue between the switch and the motor. Unfortunately the plug harness to the motor cables is under the seat in a black plastic containment shelf making it extremely difficult to unplug and the routing of the cables does not seem to allow for withdrawing the motor cables to test the motor or reposition the seat with a 12v supply to the motor; requiring removal of the seat to access the motor connectors.

Is there any way to free up the fore/aft motor assembly to at least gain manual fore/aft movement of the seat?

Any other means of seat removal that you can think of in a situation like this where you cannot access the forward mounting bolts nor move the seat electrically to do so?

Any tips on removing the plastic trim around the seat base? It's old brittle and does not seem visually obvious as to how it comes off nor can I find the details in the FSM.

All suggestions welcomed, TIA

Stretch · #2 11-29-2018, 11:16 AM

Is it not just four bolts per seat at the ends of the rails?

87tdwagen · #3 11-29-2018, 11:25 AM

Hi Stretch, yes there are 4 bolts that hold the seat rails to the floor pan, I have access to the rear 2, but cannot access the front two due to the seat positioned over the front rails. I cannot access the seat motor harness to try to apply 12v to the motor directly to see if the motor is bad or to move the seat to access the front rail bolts.

Assuming worst case scenario, where the motor is bad, how can I remove the seat in this situation?

Can the fore/aft motor (I believe it is the middle of 3 motors in the motor pack under the seat) be removed from the seat track? If so would this disengagement allow me to manually move the seat along the tracks, or is there something that I need to also disconnect?

Stretch · #4 11-29-2018, 12:49 PM

I'm having trouble reaching the FSM on startekinfo too so I can't send you a link to a PDF

I was hoping to find the correct chapter - could be in with the seats or because of the electrickery element in the equation in the electrical components section

I've had a similar problem when a seat was stuck (not electric) and managed to get a 12 point ring spanner on the head and undid it very slowly. Is there any chance that could be done in your situation?

87tdwagen · #5 11-29-2018, 02:41 PM

The issue I have with the front bolts is not being able to access them with the seat track forward as it is, see pic 1:

Also was thinking of possibly disconnecting what seems like 4 curved pivot arms for the raise/lower tilt arms to separate the seat from the track assembly to gain better access. These bolts are horizontal as shown in the image below in yellow, but the concern there is feeling around the backside they appear to have nuts on the bolts and those are inside the seat track channel, cannot get a spanner on them to hold as I unbolt and not sure if the nuts are welded to the track frame or if they come free. There is a plastic shelf that contains the connector plugs shown in red, it looks like this shelf can come out which would at least give me access to the connectors for some motor testing, but I cannot figure out how to release the plastic tray and pull it out rearwards from under the seat.

Stretch · #6 11-30-2018, 02:25 AM

If you google the problem you get a few mercedes source videos where they're trying to get you to buy a 13 dollar video on how to fix this problem.

One of the snippets is to get to the plugs and try to power the motors directly. You say the plugs are hard to reach in your first post but you might want to try and do this at the switch?

JimFreeh · #7 11-30-2018, 11:38 AM

If the height adjuster still functions, can you raise the seat to gain a bit more room?

Next thought would be to remove the switch and jump the wire.

Or, replace the switch?

I recall that the trim is snap on, break off.

Jim

87tdwagen · #8 11-30-2018, 12:16 PM

Thanks for the suggestions, keep them coming.

I have tested the door switch and also have 4 spares that are known, all perform the same way, all set functions work with the exception of fore/aft.

I have also applied 12v and Grnd directly to the connector at the back of the door switch pins 4&6 of the 6 prong plug which are for the fore/aft motor and no movement.

As mentioned earlier, even though the tilt function works and the seat is as far up as it will go, the plug connectors for the motor pack under the seat are retained inside a plastic shelf/box with the cables looped under the front side, this means I cannot disconnect these connectors to test the motor or conductivity between the door switch and motor unless I can get this shelf out from under the seat or remove the seat to access.

I'm assuming at this point that I either have a broken connection between the switch and the motor or the motor itself is bad. As much as I hate to have to cut into the cables to test continuity (prefer to do at connectors) I may not have any other choice.

I am willing to remove the seat in favor of cutting into the harnesses, if there is some way to separate the seat from the track assembly, that can be done in this case. I know that the seat frame (box spring) is bolted to the track assembly via 6 screws, but there is no way I can do this without being able to more the seat fore/aft either electrically or manually due to having to align the holes in the frame rail with the screw heads 1 par at a time, x 3 times.

Any ideas of how to remove that plastic shelf containing the motor to harness connectors from under the seat?

Any ideas on how to separate the seat from the track assembly with no fore/aft movement?

Lastly, is there any way to detach the fore/aft motor from the track to gain manual control over the fore/aft movement, allowing the seat to free wheel so to speak?

Thanks again

87tdwagen · #9 12-01-2018, 06:43 PM

Well after spending some more time studying the removal of the seat, I thought I had it nearly figured out when the seat belt rail defeated me... I could access the rear mount but not the forward one on the driveshaft/trans tunnel, and this alone seemed an impediment. I was willing to dig out the sawsall and sacrifice the seat belt rail as that could be readily found in a junk yard cheap.

Before cutting anything, and as a means of venting my frustration, I went for the hammer instead....the seat was not gonna win without a fight...a few raps on the fore/aft seat motor, just to show it who's boss and wouldn't you know it....it worked

Restored function whoopee!

Must need some a good going through cleaning and relubed. Now that the seat moves I should be able to remove it the normal procedure and can then address cleaning and lubricating the motor pack.

A few things learned worth noting:

If your seat motor isn't working, and all other wiring and switch issues have been ruled out, give it a rap with a hammer or suitable wrench and see if that works, it just might.

Secondly, should the motor indeed be dead, the seat can be separated from the motor/rail chassis via the lift arm mounting bolts(4) 2 front, 2 rear. 3 of the four bolts engage a boss in the track rail, the forward innermost bolt does have a nut on the back of it, if the seat is forward, you can get a wrench on the nut, if the seat is seat rearwards, you're likely SOL.

The only hangup to separating the seat this was, the seat belt receiver and rail. It may be possible to undo the seat belt receiver via it's mounting bolt to the retaining metal strap and finagle it out (possible on my 87) thus taking the seat belt receiver out with the seat but leaving the seat belt rail mounted to the tunnel; or it may be captured by another metal strap that loops it under the track making it impossible to separate (my 94) necessitating cutting the seat belt receiver rail along the tunnel. Luckily the hammer worked

Thanks to all for your suggestions and help